404 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



without sculptim? except lines of growth; hinule large, cordate, cir- 

 cumscribed by an incised line, lamellose, the apposited edges slightly 

 pouting; escutcheon bordered by a sharp keel in the left and a rounded 

 rido-e in the right vahe; wider and smooth in the left, narrower and 

 more or less lamellose in th(> right valve, the latter slightly overlap- 

 ping behind; ligament sunken but not covered; the concentric sculp- 

 ture slightly more prominent distally; interior white, the margins 

 tinely crenulate; the pallial sinus short, wide, angular, reaching for- 

 ward only to the vertical of the posterior end of the ligament; hinge 

 strong, the posterior pair of right cardinals and the middle left one 

 subsulcate; anterior lateral distinct. Length, -tl; height, 36; diame- 

 ter, 23 mm. 



Purchased with a lot of west coast beach shells at Acapulco, Mexico, 

 in 1868, by W. H. Dall. Cat. No. 103286, U.S.N.M. 



This looks almost exactly like a young quahog, externall}', and the 

 Cytherea hinge is a surprise. Only one specimen has been examined. 

 It agrees with dealer's shells which come to me named foveolata 

 Sowerby, a species which so far seems positively located only in the 

 Cape Verde Islands. 



CYCLINELLA SINGLEYI, new species. 

 Plate XV. fi^-. M. 



Shell suborbicular. white, shining, but not polished, covered with 

 fine, sharp concentric striation and marked with obscure obsolete radial 

 lineation; valves convex, slightl}" flattened on the posterior dorsal 

 slope; beaks small, pointed, slightly anteriorly twisted; lunule lan- 

 ceolate, defined by an impressed line; ligament long, strong, deeply 

 inset; interior white, earthy, with entire margins and a deep, angular 

 pallial sinus, pointing toward the umbo of the shell. Length, 39; 

 height, 38; diameter, 23 mm. 



Collected near the delta of the Yaqui River, West Mexico, ))y J. A. 

 Singley. Cat. No. 108817, U.S.N.M. 



This is a more inflated, more sharply scidptured, and more shining 

 species than any of the others. 



CHIONE (LIROPHORA) SCHOTTII, new species. 



Plate XVI, fig. 7. 



Shell small, white, rounded-trigonal, with high, pointed, slightly 

 recurved beaks; lunule long, lanceolate, narrow; escutcheon, limited 

 by an inconspicuous keel, nearly smooth; .sculpture of close-set subcon- 

 centric, flattened ribs, separated only by much narrower sulci, and not 

 always in harmony with the incremental lines; these ribs are abruptly 

 attenuated or l)ifurcate on the posterior dorsal area; there is no trace 

 of any radial sculpture; interior white; pallial sinus small and rather 



