802 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XX. 



rather elongated lateral tootb ; the left valve also lias a small, elongated, 

 tooth-like expansion posterior to the cartilage-plate. 



Length, 4.5 mm.; height, 2.25 mm.; breadth, 1.5 mm. 



This species may easily be mistaken for the young of C. obesa and C. 

 fraterna; the structure of the hinge is, however, characteristic. 



A comparatively few specimens, at seven station, between N. lat. 

 41 28' 30", W. long. 65 35' 30", and 35 49' 30", W. long. 74 34' 45", 

 in 515 to 1,290 fathoms, 1883-1886. 



CUSPIDARIA VENTRICOSA, new species. 

 (Plates LXXII, fig. 5; LXXVI, fig. 6.) 



Shell large, rather solid, swollen, with a ventral enlargement and a 

 moderately elongated, tapered rostrum. Umbos swollen and promi- 

 nent; beaks incurved. Antero-dorsal margin at first nearly straight, 

 then broadly rounded with the extreme anterior end a little prominent; 

 ventral margin decidedly excurved in the middle, corresponding to the 

 exterior swelling; at the base of the rostrum slightly concave; postero- 

 dorsal margin somewhat concave, the most so at the base of the ros- 

 trum, which is obtusely rounded at the end. Exterior covered with very 

 distinct lines of growth and irregular, stronger, concentric grooves. 

 C-i the rostrum there is an obtuse, diagonal ridge running to the ven- 

 tral angle of the tip; between this and the dorsal margin there are two 

 others less distinct. The anterior hinge-margin is decidedly thickened 

 in both valves and projects inward with a thick, rounded edge, most 

 conspicuous in the right valve, in which it is abruptly much narrowed 

 near the cartilage-plate; in this valve the lateral tooth is short, stout, 

 obtuse, very prominent, and situated close to the beak, its length along 

 the margin not much exceeding its height; cartilage-plate small, rela- 

 tively wide, oblique, directed backward and downward, and closely 

 united to the lateral tooth, there being only a slight, rounded notch 

 between. 



Length of the larger specimen, 30 mm.; height, 29 mm.; breadth, 18 

 mm.; beak to end of rostrum, 16 mm.; beak to anterior end, 17 mm. 

 Another specimen is 25 mm. long; 17 mm. high; 12 mm. broad. 



Four valves, at three station, between N. lat. 40 29', W. long. 66 4', 

 and K lat. 38 27' 30", W. long. 70 54' 30", in 349 to 1,769 fathoms, 

 1882-1886. 



This species has some resemblance to C. glacialis, but is a stouter and 

 more swollen shell, with a relatively larger rostrum, much more elon- 

 gated and less prominent lateral tooth, and very different cartilage- 

 plate. The latter does not have the swollen ventral region, character- 

 istic of our species, nor the diagonal ribs on the rostrum. 



