PELECYPODA 569 



straight; teeth prominent, 23 on anterior and 18 on posterior side: 

 North Carolina to Labrador in shallow water; common; Pacific coast; 

 Europe. 



Y. sapotilla (Gould). Like the above but much smaller, and with 

 about 16 teeth on each side ; 22 mm. long, 11 mm. high and 7 mm. wide : 

 Long Island to Arctic Ocean ; often common, in 4 to 120 fathoms. 



Y. thraciaeformis Storer. Shell reniform, rounded and broadest 

 behind, gaping at both ends; 5 cm. long; 4 cm. high, and 27 mm. wide; 

 hinge with about 12 teeth on each side: Long Island to Arctic Ocean; 

 in rather deep water. 



3. LEDA Schumacher. Shell elongated, the hinder part being much 

 prolonged; mantle open, with small, united siphons: 80 species, cosmo- 

 politan. 



L. tenuisulcata (Couthouy) (Fig. 894). Shell 25 mm. long, 12 mm. 

 high, and 7.5 mm. wide, light greenish-yellow in color, with 12 anterior 



Fig. 893 Fig. 894 Fig. 895 



Fig. 893 Yoldia limatula (Verrill). Fig. 894 JLeda tenuisulcata (Gould). 

 Fig. 895 Solemya, velum (Verrill). 



and 16 posterior teeth: Rhode Island northwards, in shallow water; 

 often common. 



FAMILY 2. SOLEMYIDAE. 



Shell equivalve, elongate, cylindrical, gaping at each end; perios- 

 tracum thick, extending over the edge of the shell; hinge toothless; foot 

 long and slender; oral palps elongate; mantle fused below, leaving an 

 opening for the foot and one hourglass-shaped siphonal opening behind : 

 1 genus. 



SOLEMYA* Lamarck (Solenomya Menke). With characters of the 

 family: several species. 



S. velum Say (Fig. 895). Shell very thin and fragile, yellowish- 

 brown in color, with about 15 impressed lines radiating from the umbo 

 to the margin, bluish-white within, 25 mm. long, 12 mm. high, and 8 mm. 

 wide: North Carolina to Nova Scotia; usually buried in the sand; also 

 found swimming backwards and forwards; often common. 



S. borealis Totten. Like the above but much larger and darker; 

 length 5 cm. ; height 22 mm. ; width 14 mm. : Long Island Sound to Nova 

 Scotia; rare. 



* See "Locomotion in Solenomya," etc., by G. A. Drew, Anat. Anz., Vol. 17, 1900. 



