43 



S. emarginatum. 



14. Spliaerium emarginatum, PRIME. Animal not observed. 

 Shell triangular, nearly equilateral, convex, tumid, 



anterior and posterior margins abrupt, posterior slightly Fig. 38. 



more distended, basal margin curved ; valves solid, in 

 terior white ; beaks very full, prominent, nearly central ; 

 ligament distinct ; sulcations regular, not heavy ; epi 

 dermis brown, with several narrow transverse zones of 

 a dark color at regular intervals ; hinge-margin curved ; 

 cardinal teeth single, quite distinct ; lateral teeth not 

 much elongated, strong. 



Long. 0.37; Lat. 0.37; Diam. 0.25 inches. 



Hob. North ,America, in the region of Lake Superior. (Cabinets of 

 Agassiz, Smithsonian Institution and Prime.) 



Cyclas emarginata, PRIME, Bost. Proc. IV, 1851, 156. 



The triangular and very tumid form of this species is quite 

 singular ; it differs from S. vermontanum in being more tumid, 

 fuller, in having larger beaks, and in being much less broad at 

 the base. The young shell is more elongated and less tumid than 

 the adult. A rare species. 



15. Spliaerium flaviim, PRIME. Animal not observed. 



Shell transversely rounded, compressed, equilateral, deli 

 cate, margins generally rounded, the posterior a little dis- ^* ^9 

 tended ; beaks central, not full, more or less depressed ; valves 



very slight, interior whitish ; sulcations pretty deep, regular ; 

 epidermis light, of a greenish-yellow color ; cardinal teeth 

 small, in the shape of the letter V reversed; lateral teeth 

 elongated. 



Long. 0.43 ; Lat. 0.31 ; Diam. 0.18 inches. 



Hab. North America, at the Sault St. Marie, Lake Superior. (Cabinets 

 of Agassiz, Smithsonian Institution, Jay and Prime.) 

 Cyclas flava, PRIME, Bost. Proc. IV, 1851, 155. 



This is a very slight and delicate species, quite distinct from 

 any others but S. patella, to which it bears some general re 

 semblance from its shape ; it is, however, more compressed, less 

 high, and the exterior of the valves is very different, as they are 

 nearly smooth in Dr. Gould s shell. Found not unplentifully in 

 the one locality. 



16. Spliaerium tumidum, W. BAIRD. S. testa ovato-trigona, 

 tumida, olivacea, conferte transversim concentrice forte costata ; umboni- 

 bus prominentibus, nee non erosis ; interne ccerulescente ; margine ventrali 

 rotundato. 



S. flavum. 



