“Eatoniella (Eatoniella) denticula n. sp.
ETYMOLOGY. Denticula—Latin. A little tooth. Refers to the shell shape.
MATERIAL EXAMINED. Types. Holotype, LACM 2658, 9 paratypes, LACM 2659; 5 paratypes, AMS C.167415. 32H 71-287. Puerto Cook, Isla de los Estados, Tierra del Fuego, Argentina. 54°45.25'S, 64°2.3'W, intertidal, Sta. 71-2-37, USARP-SOSC-R/V Hero Cr.712, 17 May 1971.
Additional Material Examined. Southern Chile: 17 73- 7 5 [8(d)]. 21 73-71 [many]. 24 75-48 [26]. Tierra del Fuego: 25 73-69 [21(d)]. 28 71-270 [13( +19d)]; 71-271 [4(+14d)]. 30A USNM H 654 [1(d)]. 30E 71-339 [2(d)]. 31A 71-274 [6]. 32B 71-295 [4]. 32D 71-293 [2]. 32G 71-311 [7]. 32H 71-287 [3]. 33A 71-258 [2(d)]; 71-308 [9(d)]; USNM H 656 [many(d)]. 33G 71-266 [9]; 73-66 [many(d)]. 33I 71-317 [17(d)]. 33J 71-264 [many(d)]. 33O 71-310 [many(d)]. (All material LACM unless otherwise indicated.)
DIAGNOSIS. Shell (Figs. 5B, C, 6C). Small (maximum length 2.0 mm), ovate-conical, moderately thick, translucent when fresh, with 2.5-3.5 teleoconch whorls. Spire with lightly convex to straight outlines, whorls lightly to moderately convex; periphery of last whorl rounded. Sutures impressed, simple. Teleoconch moderately smooth with faint growth lines. Protoconch (Fig. 6C) smooth, of 1.2-1.7 whorls. Aperture subcircular, weakly angled posteriorly, with moderately sharp peristome, lacking external varix. Inner lip narrow, outer lip moderately prosocline. Umbilical chink very small. Periostracum very thin, transparent. Color pale grey to pale yellowish-white, fading to white.
Dimensions.
SL
SW
SL/SW
AL
SL/AL
TW
PW
PD
Holotype
1.78
1.13
1.65
0.68
2.73
3.1
1.4
0.40
Paratypes
1.83
1.14
1.60
0.68
2.67
2.7
1.6
1.43
1.74
1.08
1.61
0.65
2.67
2.8
1.5
0.42
1.67
1.04
1.61
0.64
2.60
2.9
1.4
0.38
1.71
0.98
1.74
0.63
2.71
2.8
1.5
0.43
1.64
0.98
1.66
0.62
2.64
2.6
1.6
0.42
1.74
1.03
1.70
0.63
2.76
2.7
1.6
0.43
1.72
1.06
1.63
0.66
2.60
2.6
1.7
0.43
1.67
0.98
1.70
0.63
2.64
2.5
1.7
0.42
1.69
0.96
1.76
0.62
2.72
2.6
1.6
0.43
Sta. 71-270
Fig. 5C
1.94
1.08
1.79
0.63
3.07
3.4
1.3
0.36
1.63
0.98
1.65
0.61
2.67
3.1
1.2
0.32
1.62
0.98
1.64
0.56
2.90
3.2
1.2
0.33
1.77
1.03
1.72
0.64
2.75
3.4
1.3
0.32
1.71
1.02
1.68
0.63
2.71
3.2
1.2
0.33
Sta. 71-311
1.90
1.16
1.65
0.63
3.02
3.4
1.3
0.32
2.04
1.21
1.69
0.63
2.77
3.5
1.2
0.33
1.99
1.17
1.71
0.66
3.00
3.2
1.3
0.36
1.81
1.07
1.69
0.64
2.82
3.0
1.4
0.41
1.71
1.04
1.65
0.57
3.02
3.1
1.2
0.34
Operculum (Fig. 7B, C). Pale yellow, oval, more strongly angled posteriorly than anteriorly, inner and outer edges approximately equally convex. Peg curved, well developed.
Radula (Fig. 8B, F, G). Central teeth with cusp formula 2-3+1+2-3 median cusp moderately long, narrow. Lateral teeth with cusp formula 2+1+2 (+ 1 outer denticle in some), primary cusp narrow, pointed. Inner marginals apparently with cusp formula 3+1+2 (somewhat obscured in mounts). Outer marginals also obscured but with at least 7-8 small cusps (based on 4 radulae).
Animal. Unpigmented or with a slight grey tinge on visceral coil.
REMARKS. The shell of this species is contrasted with E. turricula above and differs from that species in its smaller shell, which has more convex whorls. The radula in the two species are similar but in E. denticula the primary cusps of the inner marginal, lateral, and central teeth are blunter and the number of cusps on the inner marginal teeth apparently smaller. Eatoniella denticula is rather similar to the Antarctic E. demissa (E.A. Smith, 1915), but the shell of the latter species is broader and the radula has more cusps on the central teeth. The shell of E. denticula is somewhat similar to the southern Australian E. victoriae Ponder and Yoo, 1978, but the shell of that species is thinner, slightly broader, and smaller.
DISTRIBUTION. Southern Chile and Tierra del Fuego in algae and among rocks; mainly intertidal with occasional specimens to 15 m. Empty shells have been found down to about 30 m. Common.Emtpy shells and a few live specimens found down to 124 m may be a different species and are listed separately; see below.”
(Ponder & Worsfold, 1994: 7-11)
