MUSEUM OF COMPARATIVE ZOOLOGY. 275 



Family VENERID^. 



Genus CYTHEREA Lamarck. 



Subgenus DIONE Megekle v. Muhlfeldt. 



Cytherea (Dione) hebraea Lamarck. 



Ci/therea hebroea Lamarck, An. s. Vert., VL p. 308, 1818. 



Habitat. West of Florida 30 fms. ; off Gordou Key 68 fms. ; Barbados, 

 100 fms. 



These specimens are all very young, and yet seem to show the characters of 

 this species sufhciently. Most of them show traces, outside of the smooth 

 colored surface, of a chalky layer which is very soon worn off and leaves no 

 trace in the adult. 



Cytherea (Dione) albida Gmelin. 



Dione albida Reeve, Conch. Icon. Dione, pi. x. fig. 39. 



A number of very small and immature valves, dredged at Stations 247 and 

 262, near Grenada, in 92-170 fms., may belong to this or some allied species. 

 They are not in a condition to be accurately determined. 



Cytherea (Veneriglossa) vesica, n. s. 



Shell thin, inflated, rounded ovate, white, uniformly concentrically grooved, 

 polished; no differentiated dorsal area; luuule wide, short, marked by a fine 

 inscribed line ; beaks tumid, involved, as in Isocardia, twisted away from the 

 hinge-line so that their tips are widely separated; margins thin, simple; hinge 

 with the teeth arranged much as in Cytherea Sayana Conrad, but with the 

 depressions prolonged into pits, the ends of the teeth sharp and pointed, and 

 the ventral margin of the hinge-shelf upturned; ligament long, in a deep 

 groove, passing away from the hinge-line under the beaks as in Isocardia ; 

 muscular impressions small, near the margin ; pallial line with a shallow 

 wide wave just before the posterior adductor scar. Lon. of shell 22.0 ; alt. 21.0; 

 diam. 17.0 mm. 



Habitat. Station 36, 84 fms., in the Gulf of Mexico ; Station 167, near Gua- 

 delupe, in 175 fms.; Barbados, 100 fms., by the "Hassler" ; all dead valves. 



This is a very singular shell. In the absence of the soft parts I am at a loss 

 to place it. If it were not for the slight wave in the pallial line, I should, in 

 spite of its Venerid teeth, have placed it in the Isocardiidre. The very young 

 shells, though more elongated and less tumid, resemble Vesicomya atlantica 

 Smith; the adults are more like it on a larger scale. The dentition is alto- 



