540 LEDIDiE. 



Fam. LEDID^E. 



Labial palps appendiculate, convoluted, very long. Mantle 

 freely open, the margins fringed and usually furnished with 

 ventral lobes ; siphonal tubes united, long, slender, and 

 completely retractile ; gills narrow, plume-like, attached 

 throughout their length. Foot compressed, slightly ge- 

 niculate, deeply grooved, forming an oval disk with crenate 

 edges. 



Shell oblong, thin, pearly within. Hinge with two teeth 

 transversely divided; ligament internal or external. 



Sub-fam. LEDIN^E. 

 Shell pearly within ; ligament internal. 



Genus LEDA, Schumacher. 



Shell equivalve, inequilateral, oblong, produced pos- 

 teriorly, closed ; surface of valves smooth or concentrically 

 striated, invested by an epidermis ; inside more or less 

 nacreous; margins smooth; beaks approximated, incurved. 

 Hinge-line angulated ; teeth divided into numerous comb- 

 like denticles on each side ; ligament internal. Pallial line 

 slightly sinuated. 



Syn. Lembulus, Risso. 



Ex. L. emarginata, Lamarck, pi. 126, fig. 4. Shell, L. 

 pernula, Midler, fig. 4, a, 4, b. 



The species of Leda have a wide geographical distribu- 

 tion, being found in deep water in the Northern and Arctic 

 seas, Siberia, Britain, Japan, Australia, the Cape, and the 

 West Indies. 



