548 MALLETIIN.E. 



Genus YOLDIA, Moller. 



Shell compressed, oblong, somewhat narrowed behind ; 

 surface of valves smooth or obliquely sculptured, covered 

 with an olive, polished epidermis ; slightly pearly within. 

 Hinge with the teeth divided into comb-like denticles; car- 

 tilage in a central pit. Pallial line deeply sinuated. 



Ex. Y. pygmsea, Miinster, pi. 130, fig. 5. Shell, Y. 

 limatula, Say, fig. 5, a, 5, b. 



The species of Yoldia are chiefly northern in their 

 geographical range, being found in the Arctic and Antarctic 

 seas, Norway, Greenland, Kamtschatka, and Massachusetts 

 in North America. The animal in Yoldia is said to be 

 destitute of the ventral lobes seen at the hind margin of 

 the mantle in Leda and Neilo. 



Species of Yoldia. 



arctica, Gray. navicularis, Couth. 



Gascoensis,Migh.andAdams. Nicobarica, Lam . 



glacialis, Gray. obesa, Stimp. 



Japonica, Adams and P^eere. pygmaea, Munst. 



laevigata, Spengl. retusa, Hinds. 



lepidula, A. Adams. sapotilla, Gould. 



limatula, Say. splendida, Phil. 



lucida, Loven. tenella, Hinds. 



Miilleri, Gray. thraciaeformis, Storer. 

 rnyalis, Couth. 



Sub-fam. MALLETIIN^E. 



Shell with the valves sometimes slightly nacreous within ; 

 ligament external. 



