. Bulletin of the Natural History Museum Zoology. 60 ALLEN, SANDERS AND F. HANNAH ture, ventral margin smoothly curved, posterior margin somewhat more convex than anterior and very slightly extended, anterior and posterior margins broad, rounded; hinge plate elongate, moderately wide except below umbo where narrow, moderately strong, acute taxodont teeth, 7 in anterior and 8 in posterior series in specimen mm; ligament internal, amphidetic, slightly elongate, barely extends below hinge plate. Prodissoconch length: 172 Maximum recorded shell length: mm. Internal morpholog
. Bulletin of the Natural History Museum Zoology. 60 ALLEN, SANDERS AND F. HANNAH ture, ventral margin smoothly curved, posterior margin somewhat more convex than anterior and very slightly extended, anterior and posterior margins broad, rounded; hinge plate elongate, moderately wide except below umbo where narrow, moderately strong, acute taxodont teeth, 7 in anterior and 8 in posterior series in specimen mm; ligament internal, amphidetic, slightly elongate, barely extends below hinge plate. Prodissoconch length: 172 Maximum recorded shell length: mm. Internal morphology (Fig. 94). The inhalent and exhal- ent siphons are combined, the inhalent is open along its ventral margin. The siphonal tentacle is either to the right or left. There is a feeding aperture and anterior to it a heavily ciliated region of the inner mantle fold. There is a well- developed anterior sense organ. The posterior adductor muscle is small and oval, the anterior adductor, also oval, is approximately twice the size of the posterior. The labial palps are moderately large with up to 19 palp ridges and each has a long thin palp proboscis. The gill which is small, dorsal in position in preserved specimens, has up to 14 plates. The visceral and cerebral ganglia are typically 'club'-shaped, the visceral being the smaller. The pedal ganglia are moderately large, elongate and situated high in the foot. The foot is long and thin with deep papillae fringing the sole. A large byssus gland is present in the heel. The stomach and style sac are small and the latter does not penetrate far into the foot. The hind gut forms double loops to the left and right of the body, recurring anterior to the stomach, thus taking a similar course to Yoldiella subcircu- laris and Yoldiella biguttata. A considerable amount of fine material was present in the digestive diverticula of the left side. The kidneys although moderately well-developed do not 50- 40- 80- 70- 60- 50- W\L H\L PL\TL \ I • ' '.
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Keywords: ., bh, bookcentury1900, bookcollectionbiodiversity, bookleafnumber62
