Skogsbergia galapagensis Kornicker & Iliffe 1989

Skogsbergia galapagensis

ETYMOLOGY.—From the collecting area.

MATERIAL.—Holotype: Sta 87–018: USNM 193420, 1 adult female in alcohol and on slide.

Allotype: Sta 87-005: USNM 193423, 1 adult male in alcohol and on slide.

Paratypes: Sta 87-005: USNM 193434, 8 specimens in alcohol. Sta 87-018: USNM 193422, 4 adult females in alcohol; USNM 193424, 1 instar I in alcohol and on slide; USNM 193425, 1 instar II in alcohol and on slide; USNM 193426, 1 instar III in alcohol and on slide; USNM 193427, 1 male instar IV in alcohol and on slide; USNM 193428, 1 female instar IV in alcohol; USNM 193429, 1 male instar V in alcohol and on slide; USNM 193430, 1 female instar V in alcohol; USNM 193431 1 adult female in alcohol; USNM 0, 18 specimens in alcohol. Sta 87-021B: USNM 1, 6 specimens in alcohol.

DISTRIBUTION.—Santa Cruz Island, Galapagos Islands: Deep Grieta east of Tortuga Bay at 6–12 m water depth; Grieta de Caleta la Torta at 10–18 m water depth (type locality); grieta north of trail to Tortuga Bay at 9–10 m water depth.

DESCRIPTION OF ADULT FEMALE (Figures 1–4c).—Carapace oval in lateral view with small incisur at midheight and narrow but distinct caudal process (Figure 13a); ventral and dorsal margins convex; tip of rostrum with minute denticulations (Figure 1c). Outer surface of valves smooth.

Infold (Figure 1b–e): Rostral infold with 1 short and 4 long divided hirsute bristles in addition to 2 divided bristles (1 long, 1 short) near inner edge of incisur (Figure 1b.c); 1 small slender divided bristle just ventral to inner end of incisur, anteroventral infold with 28–34 spinous divided hirsute bristles forming row just distal to narrow list (Figure 1b); ventral infold with 3–6 widely separated short bristles along narrow list; left valve only with bristle at midwidth of ventral infold just anterior to caudal process; list broadening anterior to caudal process and forming inner margin of infold, with 3 or 4 small bristles and numerous pores perpendicular to list and leading to its posterior edge (Figure 1d,e). 7–10 minute pores forming row along outer edge of infold of caudal process; 2 or 3 minute pores near outer edge of caudal process visible through infold and leading to slender bristle on outer surface of valve (Figure 1d,e). Right valve with sclerotized bar along inner edge of posterior infold dorsal to caudal process (Figure 1e)

Selvage (Figure 1b): Selvage without fringe. Anterodorsal selvage along rostrum narrow, broadening and becoming narrowly striate along dorsal and ventral edges of incisur, dividing at inner end of incisur, narrow along anteroventral and ventral margins of valve, and absent along outer edge of caudal process and posterior edge of valve.

Size: USNM 193420, length 2.09 mm, height 1.36 mm; USNM 193431, length 2.02 mm, height 1.35 mm. USNM 193422, 4 specimens: length 2.07 mm, height 1.38 mm; length 2.10 mm, height 1.35 mm; length 2.14 mm, height 1.40 mm; length 2.04 mm, height 1.41 mm.

First Antenna (Figures 1f,g, 3g): 1st joint bare. 2nd joint spinous. 3rd joint short with medial spines forming rows and 2 short spinous bristles (1 ventral, 1 dorsal). 4th joint with 2 short spinous bristles (1 ventral, 1 dorsal). Stout sensory bristle of 5th joint with 9 long filaments followed by 3 short filaments and 1 smaller filament (long filaments with minute terminal papillae; short filaments and tip of bristle with minute terminal spine) (Figure 1g). 6th joint with short medial bristle near dorsal margin. 7th joint: a-bristle about same length as bristle of 6th joint, with few marginal spines; b-bristle about 4 times length of a-bristle, with 3 short filaments followed by 2 longer filaments (filaments with few marginal spines; bristle and filaments with terminal spine); c-bristle about ⅓ longer than sensory bristle of 5th joint, with 8 short filaments followed by 1 longer filament and 1 very small subterminal filament (some filaments with short marginal spines; filaments and bristle with terminal spine). 8th joint: d- and e-bristles about same length as b-bristle, with blunt tips; f-bristle long (tip broken off on holotype), with 7 marginal filaments, some with marginal spines); g-bristle long (tip broken off on holotype) with 10 marginal filaments, some with marginal spines.

Second Antenna (Figure 2a–c): Protopodite with short spinous distal medial bristle. Endopodite 2-jointed: 1st joint with 3 bare proximal bristles (1 long, 2 short) and 1 spinous distal bristle (about same length as long proximal bristle); 2nd joint short, with long terminal filament with blunt tip (Figure 2a). Exopodite (Figure 2b,c): bristle of 2nd joint reaching 9th joint, ventral margin of bristle with about 6 stout spines (3rd or 4th spine from proximal end stouter) followed by 2 slender spines and stout subterminal spine; dorsal margin of bristle with few slender proximal spines; tip of bristle with narrowly ringed segment; bristles of joints 3 and 4 with slender proximal ventral spines and broad spine-like ventral hairs at midlength followed by slender natatory hairs (Figure 2c); bristles of joints 5–8 with natatory hairs; 9th joint with 4 bristles (3 long with natatory hairs, 1 small with few short hairs); joints 3–8 with slender sharply pointed basal spines increasing in length on distal joints (spine of 8th joint reaching past distal margin of 9th joint) (Figure 2b); 9th joint with small lateral spine near dorsal margin.

Mandible (Figure 2d,e): Coxale endite spinous with 2 stout terminal prongs with small process between them; minute bristle near base of endite. Basale: ventral margin with 3 small a-bristles (distal unringed), 1 small lateral b-bristle, 2 spinous c-bristles, 1 long spinous d-bristle, and 1 minute medial bristle just proximal to c-bristles; dorsal margin with 1 bristle (with few spines) at midlength and 2 subterminal (bare or with few spines). Exopodite about ¾ length dorsal margin of 1st endopodial joint, hirsute distally, with 2 subterminal bristles (proximal bristle spinous, about twice length distal bristle). 1st endopodial joint with 4 ventral bristles (2 long, 1 short, 1 minute). 2nd endopodial joint: ventral margin with bristles forming 3 groups comprising 1, 1, and 2 short slender bristles (lateral bristle of distal pair shorter than medial bristle); dorsal margin and medial surface near dorsal margin with about 14 short bristles (not all shown on illustrated limb), 1 or 2 slightly longer bristles, and 6 long bristles (some with bases on lateral side); medial surface with spines forming rows. 3rd endopodial joint with 3 short claws (medial and lateral claws with stout proximal spines (Figure 2e); shorter dorsal claw bare) and 4 bristles (ventral bristle short; no bristles swollen near base).

Maxilla (Figure 2f–j): Endites I–III with about 10, 7, and 6 bristles, respectively; 1 short bristle near base of endite III (on basale?) (Figure 2f). Precoxale and coxale with dorsal fringe of long hairs; coxale with hirsute dorsal bristle with long proximal and short distal hairs (Figure 2i). Basale with 3 distal bristles: 1 short dorsal, 2 ventral (1 medial short, 1 long lateral). Exopodite with short proximal bristle with base close to 2 terminal bristles (proximal bristle with long proximal hairs; outer terminal bristle with long hairs followed by shorter hairs) (Figure 2j). 1st endopodial joint with 2 bare alpha-bristles, 2 beta-bristles (outer pectinate, inner with few hairs), and smoothly rounded terminal tooth on inner margin (Figure 2g). 2nd endopodial joint with 4 a-bristles with few proximal spines (Figure 2h), 3 or 4 pectinate b-bristles (presence of 4th b-bristle on right limb probably aberrancy), 2 pectinate c-bristles, and 3 stout pectinate d-bristles (Figure 2g).

Fifth Limb (Figure 3a–c,f): Sclerotized anterior process of protopodite elongate, undulate, with smoothly rounded tip (Figure 3b). Endites I and II each with 5 or 6 bristles; endite III with 6 or 7 bristles. 1st exopodial joint: anterior side with 1 proximal bristle (with long proximal and short distal spines) near process of protopodite and 3 distal bristles forming row (outer bristle stout with long proximal spines and pectinate distally; inner bristles with long proximal and short distal spines); main tooth comprising triangular peg followed by 6 pectinate teeth; bristle with long proximal hairs and short distal spines present proximal to peg of main tooth. 2nd exopodial joint with 4 stout pectinate unringed a-bristles, 6 pectinate b-bristles (ringed distally), c-bristle with long proximal and short distal spines, and long anterior d-bristle with long proximal and short distal spines. 3rd exopodial joint with 3 bristles on inner lobe and 2 on outer lobe (on left limb of USNM 193420, both bristles of outer lobe with long proximal hairs, on right limb only outer bristle with long hairs); fused 4th and 5th joints with 4 or 5 bristles.

Sixth Limb (Figure 3d,e): Endites with total of 16–19 bristles: endite I with 3 or 4 bristles (1 or 2 short proximal, 2 longer terminal); endite II with 3 or 4 bristles (1 or 2 short medial proximal, 2 terminal); endite III with 4 or 5 bristles (0 or 1 medial proximal, 4 terminal); endite IV with 5–7 bristles (1 medial proximal, 4–6 terminal). End joint with 13–15 bristles (posterior 2 plumose, others with long proximal hairs and short distal spines, or only short spines). Stem with 3 or 4 bare epipodial bristles.

Seventh Limb (Figure 1h): Each limb with 18 or 19 bristles (12 in terminal group, 6 on each side, and 6 or 7 in proximal group, 3 or 4 on each side), each with up to 7 bells (most with 4 bells, 2 with only 1 bell). Terminal comb with 11 teeth (3 long teeth in middle, and on each side 4 shorter teeth with rounded tips and 2 short teeth with square tips). Surface opposite comb with 4 minute teeth (2 on each side; only closer 2 shown on Figure 1h).

Furca (Figure 3f): Each lamella with 10 claws; claw 2 broader distally than claw 1 but about same width at base; claw 5 slightly broader than claw 4 but about same length, and narrower as well as shorter than claw 3; claw 2 with weak basal suture defined best at anterior and posterior ends; claw 1 with slender teeth along posterior edge and stouter medial teeth forming row with stouter teeth at claw midlength; remaining claws with slender teeth along posterior margin forming lateral and medial row; right lamella slightly anterior to left and with few indistinct spines along anterior margin.

Bellonci Organ (Figure 3g): Elongate with tapering tip.

Eyes: Medial eye small, unpigmented (Figure 3g). Lateral eye indistinct, unpigmented, minute, with globular cells but no ommatidia (Figure 1i).

Upper Lip (Figure 4a,b): Anterior part undivided and with glandular openings along both anterior and ventral margins; posterior part paired and with ventral glandular openings; 2 small lobes with few glandular openings present lateral to posterior end of each paired part; posterior of lip rounded hirsute.

Genitalia (Figure 3h): Comprising ring on each side of body.

Anterior of Body (Figures 3g, 4a): Single sclerotized process with pointed tip present between upper lip and medial eye.

Posterior of Body (Figure 4c): Bare and without dorsal process. Posterodorsal margin dorsal to sclerotized internal girdle slightly scalloped in lateral view with indentations caused by banded muscles (not segmented).

Y-Sclerite (Figure 3h): Typical for subfamily.

Eggs: No ovigerous females in collection.

Gut Content: 5 specimens (USNM 193420, 193422) with gut gorged with fine grained unidentified substance appearing white in reflected light and light amber in transmitted light.

DESCRIPTION OF ADULT MALE (Figure 4d–k).—Carapace similar to that of adult female but smaller, and rostrum more rounded (Figure 4d,e).

Infold (Figure 4f,g): Bristles of rostrum and caudal process similar to those of adult female. Anteroventral infold with 24 bristles forming row.

Size: USNM 193423, length 1.76 mm, height 1.10 mm.

First Antenna (Figure 4h,i): Joints 1–6 similar to joints of adult female except for smaller ventral bristle on 4th joint 7th joint: a-bristle small, similar to that of adult female; b-bristle about 7 times length of a-bristle, not as long as sensory bristle of 5th joint, with bulbous base bearing both short filament (with large transparent sucker at midlength and small subterminal node) and stem with 2 slender marginal filaments (proximal with 6, distal with 8 minute suckers), followed by 2 slender marginal filaments (each with about 4 minute marginal spines), and minute terminal papilla; c-bristle almost twice length of b-bristle, with bulbous base bearing both short filament (with large transparent sucker at midlength and small subterminal node) and stem with 2 slender marginal filaments (each with 8 minute suckers), followed by 6 long slender marginal filaments (some with few marginal spines) and short subterminal filament; tip of stem blunt. 8th joint: d- and e-bristles slightly shorter than b-bristle, bare with blunt tips; f-and g-bristles about same length as c-bristle, both with many long proximal hair-like filaments followed by about 7 stouter filaments and terminal papilla.

Second Antenna: Protopodite with short spinous distal medial bristle. Endopodite 2-jointed (similar to that of adult female): 1st joint with 3 proximal bristles (1 long, 2 short) and 1 spinous distal bristle (slightly shorter than long proximal bristle); 2nd joint small, with long terminal filament. Exopodite without medial terminal bristle on 1st joint (also absent on adult female); bristle of 2nd joint reaching just past 9th joint, ventral margin with few long proximal hairs followed by 4 stout spines, 2 slender spines, 1 stout subterminal spine, and terminal papilla; bristles of 3rd and 4th joints with broad flat spear-like ventral hairs proximal to midlength (similar to those of same bristles of female); remaining characters similar to those of adult female.

Mandible: b-bristle of basale absent on left limb of USNM 193423, but present on right limb (possibly, absence of b-bristle on left limb aberrant); dorsal margin of 2nd endopodial joint with 21 bristles (14 spinous bristles forming medial row along edge of joint, 2 longer spinous bristles (about twice length short bristles) lateral to short bristles, and 6 long bristles (some with few spines) along edge of joint or on lateral side near dorsal margin; limb otherwise similar to that of adult female.

Maxilla: Similar to that of adult female. 2nd endopodial joint with 4 a-bristles, 3 b-bristles, 2 c-bristles, and 3 d-bristles.

Fifth Limb: Epipodite with 53 plumose bristles. Endite I with 6 bristles, endite II with 5 bristles, endite III with 7 bristles. Exopodite similar to that of adult female.

Sixth Limb: Epipodite with 4 bristles. End joint with 12 bristles. Endite bristles not counted.

Seventh Limb: Left limb of USNM 193423 with 23 bristles (15 in terminal group, 7 or 8 on each side, and 8 in proximal group, 3 on comb side, 5 on opposite side); bells on bristles similar to those of adult female. Comb and surface opposite comb similar to adult female.

Furca (Figure 4j): Similar to that of adult female except claws appearing slightly more slender.

Bellonci Organ (Figure 4k), Posterior of Body, Y- Sclerite: Similar to those of adult female.

Eyes: Medial eye small unpigmented (Figure 4k). Lateral eye indistinct, transparent, with small amber-colored cells (Figure 4k).

Upper Lip (Figure 4k): Four small glandular openings forming row proximal to small posterior lateral lobe; lip otherwise similar to that of adult female.

Genitalia (Figure 4j): Copulatory organ well developed, lobate.

Anterior of Body (Figure 4k): Single process with 2 small triangular processes on tip.

Gut Content: Gut with unrecognizable minute light amber-colored particles.

DESCRIPTION OF INSTAR I (Sex unknown) (Figures 5–6c).—Carapace similar to that of adult female except being more elongate and with relatively broader caudal process (Figure 5a). Tip of rostrum digitate as on adult female. Narrow curved line (ridge?) extending from upper edge of inner end of incisur and intersecting anteroventral valve edge as on adult female.

Infold: Infold of rostrum similar to that of adult female, with 4 long bristles, 1 short bristle near inner end of incisur, and paired bristles near valve edge at inner end of incisur. Inner edge of infold and list well defined, similar to those of adult female. Anteroventral infold with 1 bristle near inner end of incisur and 11 bristles forming row just distal to list. Broad list of caudal process similar to that of adult female. Ventral infold with 2 bristles (1 near middle, 1 near caudal process). Right valve with bar dorsal to list of caudal process similar to that of adult female.

Selvage: With lamellar prolongation similar to that of adult female.

Size: USNM 193424, length 0.78 mm, height 0.53 mm.

First Antenna (Figure 5b,c): 1st joint bare. 2nd joint with distal medial and lateral spines. 3rd joint with 2 short bristles (1 ventral, 1 dorsal). 4th joint bare. Sensory bristle of 5th joint without marginal filaments and with minute terminal papilla. 6th joint with short medial bristle with few marginal spines. 7th joint: a-bristle about same length as bristle of 6th joint, with few marginal spines; b-bristle bare, about 4 times length of a-bristle; c-bristle long, bare. 8th joint: d- and e-bristles longer than b-bristle, bare with blunt tips; f-bristle long, bare, bent dorsally; g-bristle long bare.

Second Antenna (Figure 5c,d): Protopodite with well-developed distal medial bristle. Endopodite 2-jointed (Figure 5d): 1st joint bare; 2nd joint about same length as 1st joint, with long terminal filament. Exopodite: joints 3–8 with minute spines forming row along distal margins; bristle of 2nd joint reaching midlength of 8th joint, with few ventral spines; 9th joint with 2 bristles, limb otherwise similar to that of adult female.

Mandible: Coxale endite spinous similar to that of adult, with small bristle near base. Ventral margin of basale with 2 a-bristles (proximal about half length distal), no b-bristle, 2 c-bristles, and no d-bristle; dorsal margin with 1 midbristle and 2 subterminal bristles. Exopodite almost reaching distal margin of 1st endopodial joint, with 2 bristles (proximal about 4 times length of distal). 1st endopodial joint with 2 long ventral bristles. Ventral margin of 2nd endopodial joint with distal spines and only 1 bristle (distance of base of bristle from distal margin of joint equal to width of joint); dorsal margin with 5 bristles (3 long, 2 short). End joint with 3 claws (lateral and medial stout and with proximal spines, dorsal more slender and bare, all about same length) and 1 ventral bristle about same length as claws.

Maxilla (Figure 5e,f): Endites I–III each with 5 spinous bristles (Figure 5e). Coxale with long slender dorsal bristle (relatively longer than coxale bristle of adult). Basale with long terminal ventral bristle. 1st endopodial joint with 1 slender alpha-bristle and 1 pectinate beta-bristle. 2nd endopodial joint with 2 a-bristles (with few proximal spines), 1 pectinate b-bristle, and 2 pectinate claw-like d-bristles; cutting tooth with 2 prongs (Figure 5f). Exopodite similar to that of adult.

Fifth Limb (Figure 5g,h): Sclerotized anterior process of protopodite very small or absent. Endites I–III with 2, 3, and 4 bristles, respectively; posterior bristle of each endite minute, bare, others spinous. 1st exopodial joint: anterior side with stout proximal bristle with long proximal spines and pectinate distally; main tooth with triangular peg followed by 1 complex pectinate tooth; spinous posterior bristle proximal to teeth. 2nd exopodial joint with 1 stout pectinate a-bristle (ringed distally), 1 long b-, or d-bristle (with long proximal spines and pectinate distally; distal teeth stronger than on d-bristle of later instars) on proximal outer edge of joint, and c-bristle with long proximal spines. 3rd exopodial joint: inner lobe not well defined, without bristles, outer lobe hirsute, with 2 bristles with long proximal hairs; fused 4th and 5th exopodial joints hirsute, with 2 terminal bristles (posterior with short marginal spines, anterior with long proximal and short distal spines). Epipodite with about 30 plumose bristles.

Sixth Limb (Figure 5i): Flap-like, hirsute, without bristles.

Seventh Limb: Absent.

Furca (Figure 6a–c): Each lamella with 5 claws; claws 2–5 without basal suture, but narrow ledge along inner edge of lamellar medial to claws 3–5 appears to be basal suture when viewed in transmitted light; claws 3 and 4 small, straight, with broad spinous base; claw 5 small blunt with terminal spines (Figure 6c); claws 1 and 2 with spines forming medial and lateral rows along posterior margins (distal medial spines of claw 1 larger); minute spines forming row along lamella posterior to claw 5; right lamella slightly anterior to left.

Bellonci Organ: Elongate, similar to that of adult female but filled with cells or globules.

Eyes: Medial eye small unpigmented. Lateral eye elongate, indistinct, filled with cells or globules (Figure 5c).

Upper Lip: Similar to that of adult female.

Anterior of Body (Figure 5j): Anterior process between medial eye and upper lip with 3 small processes.

Posterior of Body (Figure 6a): Posterodorsal corner with small process with few long hairs.

Y-Sclerite (Figure 6a): Posterior end fused to other sclerites; anterior end without ventral branch.

Gut Content: USNM 193424 with mostly unidentifiable particles but also with few fragments bearing claws suggesting arthropod origin.

DESCRIPTION OF INSTAR II (Sex unknown) (Figure 6d–l).—Carapace similar to that of adult female except caudal process relatively broader (Figure 6d). Tip of rostrum with minute single process (not digitate as on adult and instar I).

Infold: Anteroventral infold with 13 bristles. Bristles of infold of rostrum, ventral margin, and caudal process similar in number to those of adult female.

Selvage: Lamellar prolongation similar to that of adult female.

Size: USNM 193425, length 0.92 mm, height 0.58 mm.

First Antenna (Figure 6e): 1st joint bare. 2nd joint with distal medial spines. 3rd joint with medial spines and 2 bristles (1 ventral, 1 dorsal). 4th joint with 1 dorsal bristle; sensory bristle of 5th joint with 3 long stout proximal filiments followed by 1 short slender filament and 1 smaller subterminal filament. 6th joint with short medial bristle. 7th joint: a-bristle slightly shorter than bristle of 6th joint; b-bristle about 3 times length of a-bristle, with 1 proximal filament; c-bristle long, with 4 long filaments followed by 1 short subterminal filament. 8th joint: d- and e-bristles about ⅓ longer than b-bristle, bare with blunt tips; f-bristle long, with 3 long filaments followed by 1 short subterminal bristle; g-bristle long, with 4 long filaments followed by 1 short subterminal filament.

Second Antenna (Figure 6f): Protopodite with medial distal bristle with short marginal spines. Endopodite 2-jointed: 1st joint with fairly long distal bristle; short 2nd joint with long terminal filament. Exopodite: bristle of 2nd joint reaching 8th joint, with about 7 ventral spines (proximal 3 stouter than others; subterminal spine long slender); 9th joint with 3 bristles (1 long with natatory hairs, 1 short and 1 minute, both with short marginal hairs); bristles of other joints and basal spines similar to those of adult female.

Mandible: Coxale endite similar to that of adult. Basale with 3 a-bristles, 1 b-bristle, 2 c-bristles, 1 minute medial bristle just proximal to c-bristles, and no d-bristle; dorsal margin of basale with 3 bristles (1 near midlength, 2 subterminal). 1st endopodial joint with 3 ventral bristles. 2nd endopodial joint: ventral margin with spines, and bristles forming 2 groups (1 in proximal group, 2 in distal group); dorsal margin with 7 bristles (3 long, 4 medium or short). End joint with 3 claws (2 stouter claws with ventral spines) and 3 bristles.

Maxilla (Figure 6g): Coxale with long slender dorsal bristle. Endite I with 7 bristles, endites II and III each with about 6 bristles; 1 short bristle on basale some distance from proximal end of endite III (an equivalent bristle on adult female is close to endite III). Basale with additional long ventral bristle near ventral margin and no dorsal bristle (proximal ventral corner obscured on both limbs of USNM 193424, and long ventral bristle could be on endite III). 1st endopodial joint with 1 slender alpha-bristle and 1 pectinate beta-bristle; cutting tooth with 2 prongs. 2nd endopodial joint with 3 a-bristles (not shown), 2 b-bristles, 1 c-bristle, and 3 d-bristles; exopodite similar to that of adult female.

Fifth Limb (Figure 6h): Sclerotized anterior process of protopodite elongate with smoothly rounded tip. Endites I and II each with 5 bristles; endite III with 6 bristles. 1st exopodial joint: anterior side with 2 distal bristles forming row (outer bristle stouter, with long proximal hairs and pectinate distally; inner bristle with long proximal and short distal hairs); main tooth of 1st exopodial joint with 1 triangular peg and 2 pectinate teeth; spinous bristle proximal to peg. 2nd exopodial joint with 3 pectinate a-bristles (proximal ringed distally), 4 pectinate b-bristles (ringed distally), c-bristle with long proximal and short distal spines, and anterior d-bristle with long proximal and short distal spines. Inner and outer lobes of 3rd exopodial joint each with 2 bristles; fused 4th and 5th joints with 2 bristles; outer lobe of 3rd joint and fused 4th and 5th joints hirsute.

Sixth Limb (Figure 6i): Single endite with 1 long bristle.

Seventh Limb (Figure 6j): Short bare thumb-like.

Furca (Figure 6k): With 5 claws; claw 2 without basal suture; claw 3 narrower and longer than claw 4.

Bellonci Organ: Similar to that of adult female.

Eyes: Medial eye small unpigmented. Lateral eye small with few light amber-colored cells, no ommatidia (Figure 6e,l).

Upper Lip: Similar to that of adult female.

Anterior of Body (Figure 6e): With anterior process similar to that of adult female.

Posterior of Body (Figure 6k): With small dorsal process with few long hairs similar to that on instar I.

Y-Sclerite (Figure 6k): Posterior end not fused to other sclerites as on instar I; anterior end without ventral branch.

Gut Content: Unidentifiable minute particles amber in transmitted light.

DESCRIPTION OF INSTAR III (Sex unknown) (Figure 7a–g).—Carapace similar to that of adult female (Figure 7a). Tip of rostrum minutely digitate.

Infold: Anteroventral infold with 15 bristles just distal to list; infold otherwise similar to that of adult female.

Selvage: Lamellar prolongation similar to that of adult female.

Size: USNM 193426, length 1.19 mm, height 0.70 mm.

First Antenna (Figure 7b,g): Joints 1–3 similar to those of instar II. 4th joint with 2 bristles (1 ventral, 1 dorsal). Sensory bristle of 5th joint with 4 long stout filaments followed by 2 short slender filaments and smaller subterminal filament. 6th joint with short medial bristle. 7th joint: a-bristle spinous, about same length as bristle of 6th joint; b-bristle 4 or 5 times length of a-bristle, with 2 short marginal filaments (1 proximal, 1 near midlength); c-bristle long, with 4 marginal filaments followed by 1 long filament and 1 short subterminal filament. 8th joint: d- and e-bristles bare with blunt tips; f-bristle long, tip broken off on specimen examined, with 5 filaments on remaining part, some with marginal spines; g-bristle long, with 5 marginal filaments followed by 1 longer filament and short subterminal filament.

Second Antenna (Figure 7b,c): Protopodite with distal medial bristle. Endopodite 2-jointed (Figure 7c): 1st joint with 2 bristles; 2nd joint with long terminal filament. Exopodite: bristle of 2nd joint reaching 7th joint; ventral margin of bristle of 2nd joint with few slender marginal spines followed by 4 stout spines followed by 4 or 5 slender spines (distal spine longer); 9th joint with 3 bristles (1 long with natatory hairs, 1 about 1/2 length of long bristle, also with natatory hairs, 1 short bare, or with few short hairs); other bristles and joints similar to those of adult female.

Mandible: Coxale endite, basale, exopodite, similar to those of adult female. 1st endopodial joint with 3 bristles (2 long, 1 short). 2nd endopodial joint: ventral margin spinous, with bristles forming 2 groups (1 in proximal group, 2 in distal group); dorsal margin with 7 bristles (4 long, 1 medium, 2 short). End joint with 3 claws and 3 bristles.

Maxilla: Endite I with 9 bristles; endite II with 6 bristles, endite III with 4 terminal bristles; 1 short bristle near base of endite III. Coxale with fringe of dorsal hairs; dorsal bristle not observed. Basale with 1 long bristle near ventral margin and 1 short dorsal bristle. Exopodite similar to that of adult female. 1st endopodial joint with 2 slender alpha-bristles and 2 beta-bristles (inner short, outer long pectinate), and poorly defined cutting tooth. 2nd endopodial joint with 3 slender a-bristles, 2 pectinate b-bristles (proximal ringed), 2 pectinate c-bristles, and 3 pectinate d-bristles (Figure 7d).

Fifth Limb: Sclerotized anterior process of protopodite elongate with smoothly rounded tip. Endite I with 6 bristles; endite II with 5 bristles; endite III with 7 bristles. 1st exopodial joint: anterior side with 1 proximal bristle near process of protopodite and 3 distal bristles forming row (outer bristle stout with long proximal spines and pectinate distally); main tooth comprising triangular peg and 3 pectinate teeth; bristle present proximal to peg. 2nd exopodial joint with 3 stout pectinate unringed a-bristles, 6 pectinate b-bristles (ringed distally), c-bristle with long proximal and short distal spines, and anterior d-bristle (with long proximal and short distal spines) proximal to 3rd joint. 3rd exopodial joint with 3 bristles on inner lobe and 2 on outer lobe. Fused 4th and 5th joints with 3 bristles.

Sixth Limb: Endite I with 1 long spinous bristle; endite II with 4 spinous bristles; endites III and IV each with 3 spinous bristles. End joint spinous, with 2 anterior bristles with long proximal and short distal spines, and 2 stouter posterior plumose bristles; 1 cpipodial bristle present.

Seventh Limb (Figure 7e) Elongate, bare.

Furca (Figure 7f): Each lamella with 7 claws; claw 2 with weak basal suture; claw 5 stouter and longer than claw 4.

Bellonci Organ (Figure 7g): Similar to that of adult female.

Eyes: Medial eye small, unpigmented. Lateral eye small with several minute amber-colored cells (Figure 7b).

Upper Lip, Y-Sclerite (Figure 7f): Similar to those of adult female.

Anterior of Body (Figure 7g: Anterior process similar to that of adult female.

Posterior of Body (Figure 7f): With dorsal process bearing long hairs.

Gut Content: Gut gorged with unidentifiable particles amber-colored in transmitted light.

DESCRIPTION OF MALE INSTAR IV (Figure 7h–m).—Carapace similar in shape to that of adult female (Figure 7h).

Infold: Bristles of rostrum and caudal process similar to those of adult female. 1 small bristle just ventral to inner end of incisur. Anteroventral infold with 18–21 bristles forming row.

Size: USNM 193427, length 1.30 mm, height 0.81 mm.

First Antenna (Figure 7j,m): Joints 1–4 similar to those of instar III. Sensory bristle of 5th joint with 5 long stout filaments followed by 3 short slender filaments and smaller subterminal filament. Sixth joint with short medial bristle. 7th joint: a-bristle about same length as bristle of 6th joint; b-bristle about 5 times length of a-bristle, with 3 marginal filaments; c-bristle long, with 6 short filaments followed by 1 long filament and short subterminal filament. 8th joint: d- and e-bristles bare with blunt tips; f-and g-bristles long, with about 5 short filaments followed by 1 long filament and 1 short subterminal filament.

Second Antenna (Figure 7i,j): Protopodite with distal medial bristle. Endopodite 2-jointed: 1st joint with 3 bristles; 2nd joint with long terminal filament. Exopodite: bristle of 2nd joint reaching 8th joint, with 8 ventral spines (proximal 4 stout, distal slender spine longer than other slender spines); 9th joint with 3 bristles (middle bristle about twice length of dorsal bristle; ventral bristle almost twice length middle bristle, all bristles with natatory hairs); remaining bristles and joints similar to those of adult female.

Mandible: Coxale, endite, basale, and exopodite similar to those of adult female. 1st endopodial joint with 3 or 4 bristles (2 long, 1 or 2 small). 2nd endopodial joint: ventral margin with bristles forming 3 groups comprising 1, 1, and 2 short slender bristles; dorsal margin with 9 bristles (4 long, 2 medium, 3 short). End joint with 3 claws and 4 bristles (ventral bristle minute).

Maxilla (Figure 7k): Coxale and precoxale with dorsal fringe; coxale with very long slender dorsal bristle. Endite I with 10 bristles, endites II and III each with 6 bristles; 1 short bristle near base of endite III (on basale?). Basale with 3 distal bristles (1 short dorsal, 1 long ventral, 1 short medial near ventral margin). Exopodite similar to that of adult female. 1st endopodial joint with 2 slender alpha-bristles and 2 beta-bristles (outer longer and pectinate), and evenly rounded cutting tooth. 2nd endopodial joint with 4 bare a-bristles, 3 pectinate b-bristles, 2 pectinate c-bristles, and 3 pectinate d-bristles.

Fifth Limb: Sclerotized anterior process of protopodite similar to that of adult female. Endites I and II each with 5 bristles; endite III with 7 bristles. 1st exopodial joint: anterior side with 1 proximal bristle near process of protopodite and 3 distal bristles forming row (outer bristle stout and with long proximal and short distal hairs); main tooth with smooth triangular peg and 4 pectinate teeth; spinous bristle present proximal to peg. 2nd exopodial joint with 3 pectinate a-bristles, 6 pectinate b-bristles, 1 posterior c-bristle, and 1 anterior d-bristle (proximal to 3rd exopodial joint). 3rd exopodial joint with 3 bristles on inner lobe and 2 on hirsute outer lobe. Fused 4th and 5th joints hirsute, with 4 bristles.

Sixth Limb: Endite 1 with 2 bristles; endite II with 3 bristles; endite III with 4 bristles; endite IV with 6 bristles. End joint with 5 anterior bristles followed by space and 3 or 4 bristles along edge of posterior half of joint (1 or 2 posterior bristles plumose, 2 anterior bristles short and with short marginal spines, others with long proximal and short distal spines). 2 epipodial bristles present.

Seventh Limb: Bristles strongly tapered. Each limb with 5 or 6 bristles (4 in terminal group, 2 on each side, and 1 or 2 in proximal group, 1 on comb side, 0 or 1 on process side); each bristle with 1 bell. Terminal comb with 7 teeth (3 long teeth in middle, and 2 short teeth on each side). Surface opposite comb with small triangular process.

Furca (Figure 7l): Each lamella with 9 claws; claw 2 with weak basal suture; claw 5 broader than claw 4.

Bellonci Organ (Figure 7m): Similar to that of adult female.

Eyes: Medial eye small unpigmented. Lateral eye small with 3–5 cells (Figure 7j,m).

Upper Lip (Figure 7m), Y -Sclerite (Figure 7l): Similar to adult female.

Genitalia (Figure 7l): Well-defined copulatory organ on each side of body anterior to furca.

Anterior of Body (Figure 7m): With anterior process similar to that of adult female.

Posterior of Body: Small dorsal process, but without hairs that were present in younger instars.

Gut Content: Gut gorged with unidentifiable particulate matter amber-colored in transmitted light.

DESCRIPTION OF FEMALE INSTAR IV (Figure 8a,b).—Carapace similar in shape to that of male instar IV (Figure 8a).

Infold: Bristles similar to those of adult female; anteroventral infold with 18 bristles forming row.

Selvage: Similar to that of adult female.

Central Adductor Muscle Attachments: Comprising both elongate and oval individual scars (not all muscles shown in Figure 8b.)

Size: USNM 193428, length 1.39 mm, height 0.88 mm.

First Antenna (Figure 8b): Joints 1–4, and 6 similar to those of male instar IV. Sensory bristle of 5th joint with 5 long stout filaments followed by 3 short slender filaments and smaller subterminal filament. 7th joint: a-bristle about same length as bristle of 6th joint; b-bristle with 3 marginal filaments; c-bristle long, with 5 short filaments followed by 1 long filament and short subterminal filament. 8th joint: d- and e-bristles bare with blunt tips; f-bristle long, with about 5 marginal filaments and shorter subterminal filament; g-bristle long, with about 8 marginal filaments and short subterminal filament.

Second Antenna (Figure 8b), Mandible: Similar to those of male instar IV.

Maxilla, Fifth and Sixth Limbs: Not examined in detail but seemingly similar to those of instar IV male.

Seventh Limb: Proximal group with 2 bristles, 1 on each side; terminal group with 4 bristles, 2 on each side. Terminal comb with 2 short teeth on each side of 3 longer teeth; side opposite comb with small triangular process.

Furca: Each lamella with 8 claws; claw 2 with weak basal suture; claw 5 broader than claw 4 but about same length.

Bellonci Organ, Upper Lip, Y-Sclerite: Similar to those of adult female.

Eyes: Lateral eye small, unpigmented, with few minute amber-colored cells (Figure 8b). Medial eye small, unpigmented.

Genitalia: None observed.

Anterior of Body: Anterior process similar to that of adult female.

Posterior of Body: Posterodorsal corner without tuft of hairs.

Gut Content: Gut gorged with unidentifiable fine-grained particles, amber-colored in transmitted light.

DESCRIPTION OF INSTAR V MALE (Figure 8d–g).—Carapace similar in shape to that of adult female (Figure 8d).

Infold: Bristles of rostrum and caudal process similar to those of adult female. Anteroventral infold with 23–27 bristles.

Selvage: Similar to that of adult female.

Size: USNM 193429, length 1.83 mm, height 1.16 mm.

First Antenna (Figure 8f): Joints 1–4 and 6 similar to those of adult female. Sensory bristle of 5th joint with 7 long stout filaments followed by 3 short slender filaments and 1 smaller subterminal filament. 7th joint: a-bristle about same length as bristle of 6th joint; b-bristle short, with 3 marginal filaments; c-bristle long, with 5 short slender filaments followed by 1 long slender filament and 1 short subterminal filament. 8th joint: d- and e-bristles bare with blunt tips; f-bristle long, with 6 marginal filaments followed by 1 shorter subterminal filament; g-bristle long, with about 6 short filaments followed by 1 shorter subterminal filament.

Second Antenna: Same number of bristles as that of adult female.

Mandible: Coxale, basale, 1st endopodial joints similar to those of adult female. 2nd endopodial joint: bristles of ventral margin similar to those of adult female; dorsal margin with 10 bristles (5 long, 2 medium, 3 short). End joint similar to that of adult female.

Maxilla: Coxale with dorsal bristle. Endite I with about 10 bristles, endite II with about 7 bristles, endite III with 6 bristles; 1 short bristle near base of endite III. Basale with 3 distal bristles: 1 short dorsal, 2 ventral (1 medial short, 1 lateral, long). Bristles of exopodite and 1st endopodial joint similar to those of adult female; cutting tooth of 1st endopodial joint evenly rounded; 2nd exopodial joint with 4 a-bristles, 3 b-bristles, 2 c-bristles, and 3 d-bristles.

Fifth Limb: Sclerotized anterior process of protopodite similar to that of adult female. Endite I with 5 bristles; endite II with 6 bristles; endite III with 7 bristles. 1st exopodial joint: anterior side with 4 anterior bristles similar to those of adult female; main tooth comprising triangular peg followed by 5 pectinate teeth; bristle with long proximal and short distal spines present proximal to peg of main tooth. 2nd exopodial joint with 4 stout pectinate a-bristles, 5 pectinate b-bristles, c-bristle with long proximal and short distal spines, and anterior d-bristle with long proximal and short distal spines. 3rd exopodial joint with 3 bristles on inner lobe and 1–2 on outer lobe; fused 4th and 5th joints hirsute, with 5 bristles.

Sixth Limb: Endites with total of 18–20 bristles: endite I with 3–4 bristles (2 short proximal, 1 or 2 long terminal); endite II with 4 bristles (2 short, medial, proximal, 1 long and 1 short, terminal); endite III with 5 bristles (1 medial, proximal, 4 terminal); endite IV with 6 or 7 bristles (1 short, proximal, 5 or 6 terminal). End joint with 10 bristles (posterior 2 plumose, others with long proximal hairs and short distal spines, or only short spines. Stem with 2 or 3 epipodial bristles.

Seventh Limb: Limb with 18 tapered bristles (terminal group with 7 on comb side and 5 on opposite side; proximal group with 3 on comb side, 4 on opposite side); 4 or 5 proximal bristles with only 1 bell, others with 3; several terminal bristles with 1 bell, others with 3 or 4 bells. Surface opposite comb not examined in detail, but of similar type to that of adult female.

Furca (Figure 8e): Each limb with 9 claws; claw 2 with weak basal suture; claw 5 stouter than claw 4 but about same length.

Bellonci Organ, Upper Lip, Anterior and Posterior of Body, Y-Sclerite: Similar to those of adult female.

Eyes: Lateral eye (Figure 8f) and medial eye similar to that of adult female.

Genitalia (Figure 8g): Small copulatory organ on each side (not identified with certainty).

Gut Content: Gut gorged with unidentifiable particles amber-colored in transmitted light.

DESCRIPTION OF FEMALE INSTAR V (Figure 8c).—Carapace similar in shape to that of adult female (Figure 8c).

Size: USNM 193430, length 1.75 mm, height 1.18 mm.

Seventh Limb: Bristles tapered, many with only 1 bell.

Furca: Each lamella with 9 claws; claw 2 of left lamella with weak basal suture, of right lamella with strong suture (aberration?). Claw 5 stouter than claw 4 but about same length.

Gut Content: Gut gorged with unidentifiable particles amber-colored in transmitted light.

COMPARISONS.—Skogsbergia galapagensis differs from previously described species referred to Skogsbergia in lacking well-developed lateral eyes. Some important morphological characters of the species of Skogsbergia are compared in Table 2. Two species that according to Poulsen (1962:162) probably should be referred to Skogsbergia are included in the table with a question, because they are insufficiently known.

REMARKS CONCERNING SEVENTH LIMB.—The 7th limbs of the preserved specimens vary in length and degree of curl. Some adult females and juveniles have fairly short 7th limbs having either curled (Figure 9c,d) or fairly straight tips. At least 1 adult female and 1 juvenile were observed to have 7th limbs about 1.5 times the length of the short type, and their tips were uncurled (Figure 9b). The single adult male in the collection has a 7th limb about 1.6 times the length of the limb of adult females having short 7th limbs, and the tip of the male limb is straight (Figure 9a). The different types of 7th limbs are shown in Figure 9 (limbs drawn at same magnification; only proximal bristles indicated on limbs). The coils are on the posterior side of the limb (clockwise when viewed from left side and counterclockwise when viewed from right side).

NUMBER OF GROWTH STAGES.—Skogsbergia galapagensis has 5 juvenile instars, the same number reported for S. lerneri by Cohen (1983:250); all growth stages of S. galapagensis are present in the collection. Five juvenile instars have been reported for 3 additional species in 3 other genera of Cypridinini: Doloria pectinata Skogsberg, 1920, by Kornicker (1969, table 1), Macrocypridina castanea Skogsberg, 1920, by Poulsen (1962:126), and Vargula hilgendorfii (Müller, 1908), by Hiruta (1980:145). No members of the Cypridinini have been reported with other than 5 juvenile growth stages. This suggests that the number of juvenile instars is constant in the Cypridinini, and that the troglobitic habit of S. galapagensis has not affected the number of growth stages.

ONTOGENY AND SEXUAL DIMORPHISM.—Except for the caudal process being slightly broader, the shape of the juvenile carapace is similar to that of the adult. The adult carapace bears an unusually low number of bristles on the rostral infold, only 7, and that number is present on all instars including the 1st. The number of bristles on the anteroventral infold increases from 11 on instar I to 24–34 on the adult (Table 9). The shape of the adult male carapace is similar to that of the adult female but is smaller (Table 10).

The order of appearance of appendages is similar to that reported for many myodocopids (Table 3): the anterior 5 limbs are already well developed in the 1st instar; in instar I the 6th limb appears as an anlage without bristles and the 7th limb is absent; the latter appears as a small bare bud in instar II and is longer but remains bare in instar III; bristles appear on the 6th limb in instar II and on the 7th limb in instar IV. The copulatory limb of the male was observed to appear in instar IV, but the female genitalia was observed only in the adult.

First Antenna (Table 4): All instars have no bristles on joints 1 and 2, 2 bristles (1 ventral, 1 dorsal) on joint 3, 1 sensory bristle on joint 5, 1 bristle (medial) on joint 6, 3 bristles on joint 7, and 4 bristles on joint 8. The 4th joint bears no bristles in instar I, 1 dorsal bristle in instar II, and 2 bristles (1 ventral, 1 dorsal) in later instars. The sensory bristle of the 5th joint is without sensory filaments in instar I, and the number of filaments gradually increase to 13 in the adult (Table 5). The b- and c-bristles of the 7th joint, and the f- and g-bristles of the 8th joint are without filaments on instar I, and have filaments in later instars. The adult male has suckers on the b-and c-bristles of the 7th joint, and abundant hair-like proximal filaments on the f- and g-bristles of the 8th joint

Second Antenna (Table 5): In all instars the protopodite bears a single medial bristle, and exopodial joints 2–8 each bear a single bristle, of which those on joints 3–8 are natatory. The endopodite is 2-jointed on all instars, but the 2nd joint is longer on younger instars, and bears a terminal filament in all instars; the 1st joint is without bristles in instar I, and the number of bristles increases gradually to 4 in instar V. The number of bristles on the 9th exopodial joint is 2 in instar I, and the number increases gradually to 4 in instar V. The appendage is similar in males and females.

Mandible (Table 6): The coxale endite is similar and the dorsal margin of the basale bears 3 bristles in all instars. The ventral margin of the basale bears 2 a-bristles in instar I and 3 in later instars, and 2 c-bristles in all instars; the lateral b-bristle and a small medial bristle proximal to the c-bristles is absent in instar I but present in other instars; the d-bristle appears first in instar III. The 1st endopodial joint bears 2 ventral bristles in instar I, and the number increases gradually to 4 in instar IV or V. The ventral margin of the 2nd endopodial joint bears 1 bristle in instar I, and this increases to 3 in instars II and III, and to 4 in later instars. The dorsal margin has 5 bristles in instar I, and this number increases gradually to 10 in instar V, then jumps to about 22 in the adult. The end joint bears 3 claws in all instars but the number of bristles increases from 1 in instar I to 4 in instar IV. The appendage is similar in males and females.

Maxilla (Table 7): Endite I bears 5 bristles in instar I, and the number increases gradually to 10 in instar IV; endite II bears 5 bristles in instar I, 6 in instars II–IV, and 7 in later instars; instar III bears 5 bristles in instar I and 6 in later instars. The exopodites are similar in all instars. The basale bears 1 bristle in instar I, and the number increases gradually to 4 in instar IV. The 1st endopodial joint bears 1 alpha-bristle and 1 beta-bristle in instar I, and increases to 2 in instar III and later instars; the cutting tooth bears 2 prongs in instars I and II and is evenly rounded in instars III or IV and later instars. The 2nd endopodial joint bears 5 bristles in instar I, and the number increases gradually to 12 in instar V. The appendage is similar on males and females.



Fifth Limb (Table 8): Endites I–III bear a total of 9 bristles in instar I, 16 bristles in instar II, and 17 to 19 in later instars. The number of anterior bristles on the 1st exopodial joint increases from 1 in instar I to 4 in instar III and later instars; the main tooth bears a proximal smooth triangular peg in all instars, 1 pectinate tooth in instar I, then the number of pectinate teeth increases by 1 tooth in each later instar (adult with 6 pectinate teeth); a spinous bristle is present on all instars proximal to the triangular peg. The 2nd exopodial joint bears 3 bristles in instar I, and the number increases gradually to 12 in the adult. The outer lobe of the 3rd exopodial joint bears 2 bristles in all instars, whereas the inner lobe bears no bristles in instar I, 2 in instar II and 3 in later instars. The fused 4th and 5th exopodial joints bear 2 bristles in instars I and II, 3 in instar III, and 4 or 5 in later instars. The appendage is similar in males and females.

Sixth Limb (Table 9): The limb in instar I is flap-like with marginal hairs but no bristles. In instar II it bears a single bristle on an endite. The number of endite bristles increases to 11 in instar III and 18–20 in instar V. The number of bristles on the end joint increases from 4 in instar III to 12–15 in the adult. The number of epipodial bristles increases from 1 in instar III to 3 or 4 in the adult. The appendage is similar in males and females.

Seventh Limb (Table 9): The limb is absent in instar I, minute in instar II, elongate but bare in instar III, elongate with tapering bristles in instars IV (5 or 6 bristles) and V (18 bristles). The adult bears 18–24 cylindrical bristles. The distal part of the limb is straight in the adult male, a small number of adult females, and a small number of instars IV and V, and is curled as well as being shorter in others. The adult male may have more bristles than the adult female (24 compared to 18 or 19, but more specimens would have to be examined to rule out variability).

Furca (Table 10): Claw 1 has a distinct basal sutures in all instars. Claw 2 is either without a basal suture (instar I) or has a weakly developed suture (instar II to adult). Except in instar I remaining claws have a distinct basal suture; in instar I claws 3–5 are without a basal suture. The number of claws increases from 5 in instar I to 10 in the adult (instars I and II have 5 claws, instar III 7 claws, instar IV 8 or 9 claws, instar V 9 claws, and the adult 10 claws). The furca is similar in males and females.

Bellonci Organ: Similar in all instars and in males and females.

Eyes: The medial eye is similar in all instars and in males and females. The lateral eye is vestigial in all instars, but is relatively slightly larger in instar I.

Upper Lip: Similar in all instars and in the adult male and female, except 4 posterior, lateral, glandular processes observed on adult male, but not on others.

Genitalia: A reduced male copulatory organ is present in instars IV and V, but female genitalia were observed only in the adult.

Anterior of Body: The anterior process has a pointed tip in juvenile instars and in the adult female but the tip bears 2 triangular processes in the male; however, as only 1 male was examined, the difference could be due to intraspecific variability.

Posterior of Body: The posterodorsal corner bears a tuft of long hairs in instars I–III, absent in later instars.

Y-Sclerite: The posterior end of the sclerite is fused to other sclerites in instar I but is separated from them in later instars. The distal ventral branch is absent in instars I and II and present in later instars.

Gut Content: The gut of the only 1st instar examined (x1500 magnification) contained small fragments bearing claws suggesting arthropod origin; no recognizable fragments were observed in later instars, but as these were examined at lower magnification (x300) it is possible that minute fragments were not resolved.

COMPARATIVE ONTOGENY.—A reason for the detailed study of the ontogeny of S. galapagensis herein is to compare the ontogeny of a troglobitic species with that of an open water species of Skogsbergia. Skogsbergia lerneri (Kornicker, 1958) was recently redescribed by Kornicker (1984:14), and its ontogeny studied by Cohen (1983). It is a species that has been collected in the Gulf of Mexico and Caribbean Sea (Kornicker, 1984:5), and has been shown by Cohen (1983:242) to be a scavenger of dead animals. Unlike S. galapagensis, which have vestigial lateral eyes, all instars of S. lerneri have well-developed lateral eyes. Both species have 5 juvenile and 1 adult instars.

Carapace: The carapace of S. galapagensis is larger than that of S. lerneri but the growth curves of both species are parallel (Figure 10). The rostral infold of the adult S. lerneri bears 32–42 bristles compared to only 7 for S. galapagensis. The anteroventral infold of S. lerneri bears 15–20 bristles inside the list compared to none on S. galapagensis. For both species, the infolds of the caudal process are similar and the carapaces of adult males are smaller than those of adult females.

First Antenna: The distribution of bristles during ontogeny is similar in both species with 1 exception: the 4th joint of the adult male S. galapagensis bears 2 bristles (1 ventral, 1 dorsal) whereas none were reported on S. lerneri by Cohen (1983, table 1). The distribution of filaments on adult females are, in general, similar for both species. The adult male of S. lerneri has 1 or 2 small suckers on each distal filament of the b- and c-bristles (Cohen, in litt., 1988) compared to 6–8 for S. galapagensis.

Second Antenna: The addition of bristles on the 9th exopodial joint is similar for both species up to the adult stage, where S. galapagensis has 4 bristles and S. lerneri 5. The addition of endopodial bristles is similar for both species.

Mandible: The development of bristles of the coxale, basale, exopodite, ventral margin of the 1st endopodial joint, and the number of claws and bristles on the 2nd endopodial joint are similar for both species. The 1st endopodial joint of instar III of S. galapagensis has 3 bristles compared to 4 for S. lerneri (Cohen, in litt., 1988). The number of dorsal bristles on the 2nd endopodial joint of the adult, is 22 on S. galapagensis and about 17 on S. lerneri.

Maxilla: The increase in numbers of alpha- and beta- bristles on the 1st endopodial joints during ontogeny is similar for both species. The number of bristles on the 2nd endopodial joint of instar II S. lerneri is 9 not 6 as was listed in Cohen (1983, table 1) (Cohen, in litt., 1988).

Fifth Limb: Only small differences occur between the 2 species in the number of bristles on the fused 4th and 5th exopodial joints. Additional differences may occur in the number of bristles on the 1st and 2nd exopodial joints, but the data presented herein and that by Cohen (1983, tables 1, 2) are not directly comparable.

Sixth Limb: The increase in the number of bristles in instars I and II are similar for both species, and differs only slightly in later instars.

Seventh Limb: Bristles appear first in instar IV for both species, and the rate of increase of bristles in later instars differs only slightly.

Furca: For both species each lamella of the furca in instar I has 5 claws, with only claw 1 having a basal suture, and in instar II each lamella bears 5 claws with all except claw 2 having a distinct basal suture. In later instars S. galapagensis bears 1 or 2 more claws than S. lerneri (the adult S. galapagensis has 10 claws, whereas S. lerneri has only 8).

Lateral Eye: The lateral eye of S. galapagensis is vestigial on all instars, but it is relatively larger in instar I (compared to size of protopodite of 2nd antenna (Figure 5c)). The lateral eye of the embryo as well as juveniles and adults of S. lerneri are well developed (Cohen, in litt., 1988).

Upper Lip: The upper lip was fully developed in instar I for both species.

Posterior of Body: For both species a tuft of hairs is present on the posterodorsal margin of instars I–III, and absent in later instars.

CONCLUSION.—Except for the vestigial lateral eye on the troglobite S. galapagenis, its morphology and ontogeny are quite similar to that of the open water species S. lerneri.

COMPOSITION.—The Halocyprida comprise the suborders Halocypridina Dana, 1853, and Cladocopina Sars, 1866. Only the former is present in the anchialine caves of the Galapagos Islands.

COMPOSITION.—The Halocypridina comprise the superfamilies Thaumatocypridoidea Müller, 1906, and Halocypridoidea Dana, 1853 (Kornicker and Sohn, 1976, fig. 2). Only the former is represented in the collection from the Galapagos Islands.

COMPOSITION.—The superfamily comprises the family Thaumatocyprididae Müller, 1906.

THAUMATOCYPRIDIDAE Müller, 1906

COMPOSITION.—This long-ranging family (Permian to Holocene) comprises 5 genera: 2 known only as fossils (Thaumatomma Kornicker and Sohn, 1976, from the Permian of Idhra Island, Greece, and Pokornyopsis Kozur, 1974, from the Upper and Lower Jurassic of southwestern and western Germany), and 3 known only from the Holocene (Thaumatocypris Müller, 1906, from off Sumatra (1100 m) and Indonesia (2000 m), Thaumatoconcha Kornicker and Sohn, 1976, widely distributed in the Atlantic, Pacific, and Indian Oceans at depths ranging from 150 to 4758 m, and Danielopolina Kornicker and Sohn, 1976, from marine caves (Cuba, Canary Islands, Bahamas, Yucatan peninsula, Mexico, Galapagos Islands) and also from the deep sea (South Atlantic, 3459 m) (Kornicker and Iliffe, in press a)).