818 PROCEEDINGS OF THE NATIONAL MUSED! . VOL. xx. 



LYONSIELLA CORDATA, new species. 

 (I'latr Xl'V, figs. 1.x.} 



Shell rather large and firm for the genus, somewhat translucent 

 bluish white, swollen, cordate, with a posterior obtuse prominence. 



I inbos prominent, turned forward spirally; beaks small, strongly 

 incurved. Lmmle small, cordate, denned only by one of the ordinary 

 tine radial ridges; the part that lies immediately under the beak is 

 deeply sunken with the edge pinched up into a prominent keel. The 

 antero-dorsal margin is strongly convex and prominent in the lunu- 

 lar region, but not so high as the umbos; the anterior margin is but 

 slightly convex and nearly perpendicular to the axis of the shell; the 

 ventral margin is strongly convex and somewhat produced iu the mid- 

 dle, farther back it is but slightly convex ; the posterior end is obtusely 

 rounded, decidedly prominent but not angular; the postero-dorsal mar- 

 gin is a little convex and slopes gradually. The surface is covered 

 with about sixty delicate, radiating, raised lines or riblets which are 

 crossed by fine lines of growth, the thin, brownish or grayish green 

 epidermis often rising into small points at their intersection, especially 

 anteriorly and posteriorly; these riblets become coarser and more dis 

 taut anteriorly, and are lacking on the lunule. The ligament is thin 

 and strong and extends backward along nearly the whole of the dorsal 

 margin and curves spirally under and around the beak in the region of 

 the resilium, so that the two come almost in contact. The hinge mar- 

 gin, in front of the beak and hmular area, is strongly convex and pro- 

 tuberant, rising nearly to the height of the umbo; posteriorly it is 

 convex and thin in both valves; in the left one it is strengthened by a 

 slight marginal rib within the ligamental furrow; both of these are less 

 evident in the right valve. There are no teeth in either valve. The 

 ossicle is relatively large, oblong, somewhat saddle-shaped, narrowest 

 and truncated anteriorly, broadest and forked posteriorly, the divisions 

 acute. The resilium beneath the ossicle is well developed, dark brown, 

 and extends forward and upward to the margin, beneath the beak. 



Length of the largest specimen, 11 mm.; height, 12 mm. Another is 



II mm. long; 11.5 mm. high; 9 mm. broad. 



Two living specimens and one valve, at three stations between !N". lat. 

 39 15', W. long. 680 8 / ? alu i N. lat. 37 38' 40", W. long. 73 16' 30", iu 

 1,423 to 1,825 fathoms, 18S4-1SXIJ. 



Family LYONSID^E. 



LYONSIA GRANULIFERA, new species. 



(Plate XCV, tig. 1.) 



Shell oblong, truncated posteriorly, narrowed and rounded anteriorly. 

 Umbo rather prominent with the beak in front of the middle and curved 

 forward; limular area considerably sunken. Anterior end evenly 



