. Bulletin of the Natural History Museum Zoology. 62 ALLEN, SANDERS AND F. HANNAH Distributed in the north eastern Atlantic, Bay of Biscay, off northwest Africa and the Azores at abyssal rise depths. Depth range: 1354-3301m. Shell description (Figs. 95-98). Shell ovate, moderately inflated, smooth with very fine concentric lines near ventral margin forming slight ridges in larger specimens, occasionally a few faint radial lines are present in larger specimens; perios- tracum pale straw-coloured, slightly iridescent; umbos very slightly anterior of midline, moderately inflated; proxim
. Bulletin of the Natural History Museum Zoology. 62 ALLEN, SANDERS AND F. HANNAH Distributed in the north eastern Atlantic, Bay of Biscay, off northwest Africa and the Azores at abyssal rise depths. Depth range: 1354-3301m. Shell description (Figs. 95-98). Shell ovate, moderately inflated, smooth with very fine concentric lines near ventral margin forming slight ridges in larger specimens, occasionally a few faint radial lines are present in larger specimens; perios- tracum pale straw-coloured, slightly iridescent; umbos very slightly anterior of midline, moderately inflated; proximal dor- sal margin straight or slightly concave on either side of umbo, antero-dorsal and anterior margin merge in an even curve in most specimens, distally postero-dorsal margin slopes down to posterior margin; posterior margin with slight angulation, poste- rior limit of anterior and posterior margins dorsal to horizontal mid-plane, ventral margin a smooth curve; hinge plate relatively narrow, barely extending to outer margins of adductor muscles, anterior hinge line relatively straight, distally slopes away from dorsal shell margin, chevron-shaped teeth small, posterior hinge line slightly curved anteriorly, with same number of teeth in each series (8/8 in a specimen mm and 12/12 in a specimen mm); ligament amphidetic, small, rounded, extends below hinge plate. Prodissoconch length: c. 190 Maximum recorded shell length: mm. There is a slight increase in the post-umbonal length as length increases, otherwise the ratios of height/length and width/length remain constant. Internal morphology (Fig. 99). The mantle edge is well- developed, particularly the inner muscular fold which at its dorsal edge, contains secretory cells beneath the main rejec- tion tract. Postero-ventral to the siphons, both the middle and inner folds are increased in size, convoluted and heavily ciliated and form a feeding aperture. Exhalent and inhalent siphons are combined, the latter be
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Keywords: ., bhlconsortium, bookc, bookcentury1900, bookcollectionbiodiversity
