. Bulletin of the Natural History Museum Zoology. Fig. 27 Yoldiella bilanta. Lateral view of the internal morphology from the right side of a specimen from Sta. 192 Cape Basin. (Scale mm). For identification of parts see Fig. 5. Shell description (Fig. 28). Shell small, ovate, not inflated, inequilateral (posterior umbonal length 54-58% of total length), in larger specimens antero-ventrally, very fine concentric lines form broadly spaced ridges, periostracum pale yellow, umbo slightly raised, inwardly directed; dorsal margin slightly convex, antero-dorsal margin curves moder- ately steeply
. Bulletin of the Natural History Museum Zoology. Fig. 27 Yoldiella bilanta. Lateral view of the internal morphology from the right side of a specimen from Sta. 192 Cape Basin. (Scale mm). For identification of parts see Fig. 5. Shell description (Fig. 28). Shell small, ovate, not inflated, inequilateral (posterior umbonal length 54-58% of total length), in larger specimens antero-ventrally, very fine concentric lines form broadly spaced ridges, periostracum pale yellow, umbo slightly raised, inwardly directed; dorsal margin slightly convex, antero-dorsal margin curves moder- ately steeply and evenly with anterior margin, ventral margin smooth curve, postero-dorsal margin slopes gently from umbo to extended posterior margin; ligament amphidetic, small, rounded, not extending below hinge plate, with small secondary anterior and posterior external extensions of fused periostracum ; hinge plate moderately long, relatively nar- row, small chevron-shaped teeth, 7 anterior and 8 posterior. Prodissoconch length: 200 Maximum recorded shell length: mm. Shell measurements (mm) & ratios are as follows:- Length Height Width H/L W/L PL/TL - - - - PL = postumbonal length Internal morphology (Fig. 29). The combined exhalent and inhalent siphons are large. The inhalent is somewhat shorter than the exhalent and open ventrally. A large sipho- nal tentacle originates on the left side of the siphonal embay- ment close to the base of the siphon. The feeding aperture is not particularly well-developed. There is a large anterior sense organ. The posterior adductor muscle is long and narrow, and only half the size of the bean-shaped anterior muscle. The gills are well-developed with up to 20 gill plates. The labial palps are relatively small with up to 12 internal palp ridges with long, thin pal
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Keywords: ., bhlconsortium, bookc, bookcentury1900, bookcollectionbiodiversity
