800 PROCEEDINGS OF THE NATIONAL MUSErV. VOL.XX. 



angular notch; while the tooth itself is relatively smaller, shorter, 

 less prominent, and more distinctly triangular in form. 



CUSPIDARIA SUBTORTA (Sars). 



(Plates LXXIII, fig. 1; LXXIV, figs. 4, 5.) 



Newra subtorta SARS, G. O., Mollusca Reg. Arcticsa Norvegise, p. 87, pi. 6, figs. 

 6, a-c, 1878. JEFFREYS, Ann. Mag. Nat. Hist., p. 234, September, 1877; I'roc. 

 Zool. Soc., London, p. 937, November, 1881. SMITH, E. A., Report Voy. Clial- 

 lenyer, Zool. Lamellibraucliiata, XIII, p. 35, 1885. 



Shell inequivalve, rather short, relatively high, much swollen in the 

 middle, with tumid umbos aud a short, tapered, somewhat upturned 

 rostrum. The anterior portion is broadly rounded, the margin forming 

 nearly a semicircle; the autero-dorsal margin is strongly convex and 

 slightly excurved; the ventral margin is evenly rounded, except at 

 the base of the rostrum where it is distinctly incurved, especially in 

 the right valve ; the postero-dorsal margin is very strongly concave in 

 the left valve and less so in the right. The rostrum is separated from 

 the body of the shell by a sinuous depression and has a poorly denned 

 diagonal ridge ; it is a little bent to the left and, when viewed from above, 

 appears slightly twisted. The surface of the shell is nearly smooth, 

 but shows distinct lines of growth anteriorly, and especially on the 

 superior part of the rostrum; the epidermis is very thin, yellowish 

 white, more or less wrinkled on the rostrum ; the hinge-margin is rather- 

 strong; the lateral tooth in the right valve is large, rather elongated, 

 rather prominent, obtusely triangular, and not separated from the very 

 small, narrow, oblique, sunken cartilage-plate by a notch; in the left 

 valve there is a small, short, prominent tooth arising from the poste- 

 rior margin of the cartilage-plate and separated from the posterior 

 hinge-margin by a distinct angular notch. 



Length, 8 mm.; height, 6 mm.; breadth, about 5 mm. 



One live specimen (No. 52545), station 2499, N. lat. 44Q 46' 30", W. 

 long. 59 55' 45", in 130 fathoms, 1885. 



This species appears to be identical with the European sitbtorta. It 

 differs from all of our other species in having a distinct tooth-like 

 tubercle behind the cartilage-plate in the left valve. The inequality 

 of the valves and the twisted rostrum give the shell a peculiar aspect. 



CARDIOMYA ABYSSICOLA, new species. 

 (Plates LXXIII, iig. 4; LXXIV, fig. 1; LXXVII, fig. 9.) 



Shell rather large, swollen, with tumid umbos ; outline elongate-ovate, 

 with a narrow, rather elongated, tapered, slightly excurved posterior 

 rostrum, the tips divergent and gaping; the anterior end is broadly 

 round, with the dorsal and ventral margins convex, the latter narrow- 

 ing gradually posteriorly with a slight sinus at the base of the rostrum ; 

 the postero-dorsal margin is concave, so that the end of the rostrum is 



