42 AMERICAN CORBICrLAD^. 



Compared with S. sulcatum it is slighter, less suleated, more 

 compressed and less tumid. This species is rare, the only speci- 

 mens I have seen were kindly presented to me by Dr. Gould. 



12. Spliaeriiiin patella, Gould. — Animal not observed. 



Shell rounded oval, lenticular, compressed, equilateral ; margins gene- 

 rally rounded ; beaks central, small, hardly raised ; valves 



Fig. 36. slight, interior white ; sulcations extremely fine ; epidermis 

 light, of a yellowish-brown color ; cardinal teeth very diminu- 

 tive, so placed as to assume the shape of the letter V reversed • 

 lateral teeth not prominent, elongated. 



S- patella. Loug_ 0,43 ; Lat. 0.31 ; Diam. 0.18 inches. 



Hab. North America, in Oregon. (Cabinets of Gould, Smithsonian In- 

 stitution and Prime.) 



Cy das patella, Gopld, Bost. Proc. Ill, 1850, 292. Atlas U. S. Exp. 

 Expedit. pi. 36. 



This species is peculiar, owing to its compressed oval shape and 

 rounded beaks ; compared with S. fiavum it is more oval, more 

 ecpiilateral, and its beaks are less tumid. The specimens in my 

 cabinet came from Dr. Gould. 



13. Spliaerium vermoiitamiiu, Prime. — Animal not observed. 



Shell very oblique, tumid, inequilateral, full ; an- 

 Fig. 37. terior margin abrupt, posterior drawn out to an 



angle, basal slightly curved ; beaks large, full, pro- 

 minent, placed very much towards the anterior, in 

 which direction they are slightly inclined ; sulca- 

 tions coarse, moderately regular ; epidermis light 

 yjj green ; ligament conspicuous ; valves solid, interior 

 \._ ^^ ^ "^ ligbt blue ; hinge-margin much curved, broad ; car- 



dinal teeth strong, representing the letter V :e- 

 5. vermontanum. ^^^.^^^ . j^^^^^j ^^^^j^ elongated. Strong. 



Long. 0.56 ; Lat. 0.37 ; Diam. 0.25 inches. 

 Hab. North America, in Lakes Champlain and Memphremagog, Ver- 

 mont. (Cabinets of Prime and Smithsbnian Institution.) 



Sphserium vermontanum, Prime, Proc. Ac. N. S. Phil. 1861, 128. 



Remarkable for its very oblique and tumid shape, and for tlie 

 abruptness of its anterior margin. Compared with S. stamineum, 

 it is more tumid and less heavily suleated ; it is less elongated and 

 more tumid than the S. striatinum. Quite rare. I have cevt: 

 seen but a few specimens of this species, which were received from 

 the late Prof. Adams, of Amherst. 



