“Ph. (Philomedes) Eugeniae n. sp.
Description: — Female: —
Shell: — Length 1.6-1.75 mm.; length : height, about 1.5 : 1; length : breadth about 1.5 : 1. Seen from the side it has its greatest height at the middle. The dorsal margin is rather strongly and almost uniformly curved, sometimes, however, somewhat less than is shown in the figure; in most cases it passes over into the anterior and posterior margins without any decided corners; sometimes, however, when the dorsal margin is less strongly arched distinct, though broadly rounded, corners may be observed. The ventral margin is uniformly arched, but less strongly than the dorsal margin; it is weakly pouting just behind the incisur. The posterior part of the shell is, at about a third of the height of the shell, drawn out into a well-marked, almost rectangular, and in most cases rather pointed, corner—sometimes, however, somewhat less pointed than in the accompanying figure. Above this corner the posterior margin of the shell is very weakly concave or almost straight. The rostrum has a rather strongly projecting, almost rectangular, but rounded, anterior corner; its ventral corner is about of the same shape as the anterior one and has an exceedingly small, almost completely reduced, spine. The incisur is rather narrow and deep, and not, as in Ph. (Ph.) globosa, Lilljeborgi and several other species of this genus, marked off from the ventral margin of the shell by a protuberance. Seen from beneath the shell is oval, with its greatest breadth at about the middle, the anterior and posterior ends being almost symmetrical, the side contours uniformly curved. The surface of the shell is, at least partly, covered with small, rounded, shallow rather close foveolae, in most cases difficult to observe, but apart from these it is quite without sculpture. It has rather sparse, scattered and rather long bristles, somewhat more numerous near the margin of the shell; these bristles are characterized by the fact that they suddenly grow narrower from a rather thick basal part (of about the same type as the long bristle in fig. 4 of Ph. (Ph.) globosa. The pores of the surface are difficult to observe, rather small and numerous. S e en from inside: Medial bristles: The bristles in the row on the rostrum are rather numerous (about the same as in figs. 2 and 6 of Ph. (Ph.) Lilljeborgi). On the posterior part of the list there is a moderate number of bristles, partly arranged in small groups. On the part of the shell between this part of the list and the margin of the shell there are a few bristles (of about the same type as in fig. 3 of Ph. (Ph.) Lilljeborgi. There is no such pocket as characterizes this latter species. The selvage on the rostrum has short, marginal hairs.
First antenna: — The three bristles on the second joint are most frequently suhequal and about as long as the fourth joint. Either all the bristles or one of the two anterior ones and the posterior bristle on the third joint were without long secondary bristles in the ease of the specimens investigated by me. The same was true of the a-bristle on the end joint. Each of the other bristles on the second to the fifth joints had only one wreath of long, stiff secondary bristles at the middle. Otherwise this antenna agrees very closely with that of Ph. (Ph.) globosa. No variation was observed in the sensorial filaments on the end bristles.
Second antenna: — Exopodite: This is very like that of Ph. (Ph.) globosa. The bristles on the second to the fifth joints are about as long as the total length of the two or three proximal joints and are furnished at about the middle with a series of about ten rather strong, smooth ventral spines. The long natatory bristles were unbroken in the females instigated by me, although some of these had rather large eggs in their brood chambers endopodite: The first joint is of the same type and has the same equipment of bristles as this joint of Ph. (Ph.) globosa. The second joint is rather elongated and has two bristles ventrally, somewhat proximally of the middle, the one situated somewhat proximally of the other. The proximal one of these bristles is rather long and has several wreaths of long, stiff secondary bristles at the middle and short hairs distally. The distal one is rather short and has only short hairs. The end bristle on this joint is somewhat longer than the joint and
finely rounded distally.
Mandible: — With regard to this limb the type-specimen showed practically complete agreement with Ph. (Ph.) globosa. In a few other specimens this limb was rather considerably more slender, and its bristles, especially those on the endopodite, were relatively shorter; on the latter specimens the secondary bristles also seemed to be more weakly developed.
In one case three bristles in addition to the two distal bristles were observed dorsally on the second protopodite joint.
Maxilla: — This is like this limb in Ph. (Ph.) globosa. The equipment of almost all the bristles is somewhat weaker than in the species mentioned. Protopodite: The bristle on the anterior side of the pale on the boundary between the protopodite and the endopodite is comparatively short, being sometimes not even half as long as the first endopodite joint; 1 has no long secondary bristles. Exopodite: Its three bristles have in most cases on a very few long secondary bristles. Endopodite: The first joint has distally-posteriorly only four bristles. The end joint has three a-bristles and three c-bristles; the d-bristles are often subequal.
Fifth limb: — This is very like this appendage in Ph. (Ph.) globosa. As a rule, however, the equipment of most of the bristles seems to be somewhat more weakly developed than in this species.
Sixth limb: — This is very like that of Ph. (Ph.) globosa; we may add that the epipodial appendage is represented only by three bristles and that the second joint of the exopodite has only seventeen to twenty bristles.
Seventh limb: — This has about the same relative length as the corresponding appendage in Ph. (Ph.) globosa. There are, as in Ph. (Ph.) Lilljeborgi and rotunda, three dorsal and two ventral cleaning bristles situated close together distally; proximally of these there are from five to seven dorsal and four to six ventral bristles scattered irregularly. The cleaning bristles are moderately long and differ somewhat in length from each other, varying also to some extent from individual to individual and on the right and the left limb of the same individual. They are furnished with three to seven bells cut off transversally distally, the tongue of the distal bell being also cut off transversally. Proximally of the bells these bristles are furnished with short, and in most cases rather fine, hairs, partly, at least, arranged in one or a few wreaths; these hairs seem sometimes to be almost entirely lacking. The end comb consists of eleven to fifteen teeth of the same type as is described for Ph. (Ph.) rotunda. The cavity dorsally of the end comb is rather deep and is furnished dorsally with two rather small, claviform, smooth chitinous pegs.
Furca: — The five posterior claws have no long basal-medial bristles. Apart from this the furca of this species agrees completely with this organ in Ph. (Ph.) Lilljeborgi.
Rod-shaped organ: — This is of precisely the same type as that of Ph. (Ph.) globosa. It is about 0.3 mm. long.
The male is unknown.
Relation to other species.
Remark: — This species is very closely related to Ph. (Ph.) assimilis G. S. BRADY, but differs it by the equipment of the endopodite of the second antenna and by having more numerous cleaning bristles on the seventh limb. In addition, unlike the species just mentioned, it has not the peculiarity that the older females break off the natatory bristles on the second antenna.
Habitat: — Tierra del Fuego: Strait of Magellan; depth, 7 m.: 3 mature females (The Swedish „Eugenie"-Expedition, 1851-1853); R.M.S., on slides. Off Cape Valentyn; 12. III. 1896; depth, 270 in.; bottom of dead shells: 1 mature female and 5 Juvenes (The Swedish Magellan Exped.); R. M. S. 135.
Type specimen: on slides in R. M. S.”(Skogsberg 1920, p. 410-413)
