. Bulletin of the Natural History Museum Zoology. 28 ALLEN, SANDERS AND F. HANNAH. Fig. 31 Yoldiella similis. Lateral view from the right side of the internal morphology of a specimen from Sta. 197. Angola Basin. (Scale = mm). For identification of parts see Fig. 5. Type specimen. Holotype: BM(NH) 1992025, Paratypes: in collection held by J. A. Allen. Material. Cruise Sta Depth No Lat (m) Long Gear Date SURINAM BASIN Knorr 25 299 1942- 54 2076 7°'N 55°'W ES Restricted to one Station on the lower slope of the Surinam Basin. Depth range: 1942-2076 m. Shell descripti
. Bulletin of the Natural History Museum Zoology. 28 ALLEN, SANDERS AND F. HANNAH. Fig. 31 Yoldiella similis. Lateral view from the right side of the internal morphology of a specimen from Sta. 197. Angola Basin. (Scale = mm). For identification of parts see Fig. 5. Type specimen. Holotype: BM(NH) 1992025, Paratypes: in collection held by J. A. Allen. Material. Cruise Sta Depth No Lat (m) Long Gear Date SURINAM BASIN Knorr 25 299 1942- 54 2076 7°'N 55°'W ES Restricted to one Station on the lower slope of the Surinam Basin. Depth range: 1942-2076 m. Shell description (Figs. 32 & 33). Shell small, ovate, moderately inflated, slightly inequilateral, surface smooth in small individuals, ridges on ventral half of shell of larger specimens, periostracum pale yellow; umbo small, slightly raised, internally directed; no lunule or escutcheon; dorsal margin convex, anterior and posterior margins slope at similar angle from umbo, anterior margin smooth curve, posterior margin slight extended and slightly subrostrate, postero-dorsal margin slightly angled at posterior limit of hinge plate, postero-ventral margin sinuous, ventral margin slightly more convex posteriorly; hinge plate strong, rela- tively long, with up to 9 anterior and 10 posterior chevron- shaped teeth, hinge plate narrow below umbo; ligament amphidetic, internal, 'goblet-shaped'. With increasing shell length, there is little change in the height to length ratio but there is a slight increase in the width to length ratio. There is also gradual post-umbonal extension with the sinuous nature of the postero-ventral margin becom- ing more conspicuous (Fig. 35). Prodissoconch length: 179 |xm. Maximum recorded shell length: mm. Internal morphology (Fig. 34). The combined siphons, the siphonal tentacle (usually on the left side), and the anterior sense organ are as in Y. similis. The adductor Fig. 32 Yoldiella sinuosa. Lateral view of a shell from the right side and detail of the
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