No. 1139. DEEP-WATER MOLLUSC A VERRILL AND BUSH. 869 



broadly rounded ami slightly produced in the middle; it joins the curve 

 of the posterior end with a scarcely perceptible incurvature in some 

 specimens; the posterior end is obtusely rounded and situated about 

 midheight of the shell. The dorsal edges of the valve are thin and a 

 little pinched up, but there is no distinct lunule and only a very nar- 

 row liguinental furrow. The epidermis is polished and somewhat iri- 

 descent, and marked witli fine, somewhat irregular lines of growth, in 

 some places showing faint, microscopic, radial striations. Color of the 

 dead valves, brownish yellow. Hinge-plate strong, narrow near the 

 beak, wide distally, strongly angled, with the outer edge naked and 

 rather broad, especially anteriorly. Teeth large and prominent dis- 

 tally, with about three small proximal ones; about eight in the ante- 

 rior and ten in the posterior series. The resilial pit is a distinct, 

 triangular fossette, or chondrophore, on the face of the margin, cover- 

 ing its whole breadth, and bordered internally by a thickened edge 

 which causes an excurvature of the margin. There is a distinct mar- 

 ginal external ligament and furrow, or escutcheon. 



Length, 4.0 mm.; height, 4.8 mm. 



Three separate valves, among Foraminifera, at station 2385, N. lat. 

 28 51', W. long. 88 18', in 730 fathoms, 1885. 



In outline this species resembles Y. curta, but differs in its wider and 

 stouter hinge-plate, more numerous and more highly developed teeth, 

 and especially in the form and structure of the resilial pit. 



YOLDIELLA INCONSPICUA, new species. 

 (Plate LXXIX, figs. 3, r>.) 



Shell small, thin, delicate, compressed, subovate; posterior end a lit- 

 tle produced and narrowed medially. Surface lustrous and iridescent. 

 Uinbos scarcely prominent; beaks small, projecting but little above the 

 dorsal margin. The antero-dorsal margin is slightly convex and nearly 

 horizontal at first, then slopes gradually to the evenly rounded anterior 

 end; ventral margin broadly rounded, slightly swollen posteriorly, 

 ascending more rapidly to the narrow and bluntly rounded posterior 

 end; postero-dorsal margin nearly straight toward the beak, then 

 slightly convex and sloping very gradually. The surface is covered 

 with fine, pretty regular, concentric grooves and raised lines, visible 

 only under the microscope. Epidermis thin, shining, iridescent, green- 

 ish yellow. The hinge-margin is thin and delicate, nearly straight; the 

 two series of teeth form a very obtuse angle at the beaks and are 

 interrupted, for a considerable space, by the resiliuin which does not lie 

 in a distinct pit. The ligament shows as a delicate, continuous mar- 

 ginal line, both in front of and behind the beaks. The teeth are small, 

 oblique, V-shaped. In the anterior series there are about six distinct 

 ones with one or two minute proximal ones; in the posterior, about 

 seven distinct ones with one or two rudimentary ones near the beak. 



