PYTHINA. 475 



tumid or compressed, closed, smooth or concentrically 

 striated ; beaks incurved, small. Hinge composed of one 

 or two primary teeth, and a lateral tooth in both valves; 

 ligament internal or sub-marginal, interrupting the hinge- 

 margin. Pallia! sinus entire. 



Si/u. Bornia, Phil. Chironia, Desk. Solecardia, Con- 

 rad. Erycina, Recluz, not Lam. 



Ex. K. suborbicularis, Montagu, pi. 114, fig. 8, 8, a. 

 Shell, K. suborbicularis, fig. 8, b, 8, c. 



The genus Kellia may at once be distinguished from 

 Lasea by an examination of the anterior tubular fold of 

 the mantle, which is closed below. The species are of 

 world-wide distribution. 



Species of Kellia. 



corbuloides, Phil. planulata, Stimp. 



eburnea, Conr. quadrata, Gould 



lactea, Brown. rugosa, Recluz. 



Leperousii, Desh. seminulum, Phil. 



railiaris, Phil. suborbicularis, Mont. 

 Petitiana, Recluz. 



Genus PYTHINA, Hinds. 



Shell trigonal ; surface of valves divaricately sculptured ; 

 beaks small, opposite. Hinge composed of a single small 

 primary tooth, and two lateral teeth in one valve ; and two 

 lateral teeth in the other; ligament external, narrow; car- 

 tilage in a linear pit extending obliquely from the beaks to 

 the base of the hinder lateral tooth. Muscular im- 

 pressions equal, rounded ; pallial line with a slight, 

 triangular sinus. 



St/Ji. Mylitta, D'Orh. and Recluz. 



