42 AMERICAN CORBICULAD^E. 



Compared with S. sulcatum it is slighter, less sulcated, 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. Spliaeriiim 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. 

 patella. Longi 0&amp;gt;43 . Lat Oi31 . D iam . 0&amp;gt;1 g i nc l les . 



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

 stitution and Prime.) 



Cydas patella, GOULD, Bost. Proc. Ill, 1850, 292. Atlas II S. Exp. 

 Expedit. pi. 36. 



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

 rounded beaks ; compared with S, flavum it is more oval, more 

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

 cabinet came from Dr. Gould. 



13. Spliaerium vermontaimm, PRIME. Animal not observed. 

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

 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 

 green ; ligament conspicuous ; valves solid, interior 

 light blue ; hinge-margin much curved, broad ; car 

 dinal teeth strong, representing the letter V re 

 versed ; lateral teeth 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 Smithsonian Institution.) 



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



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

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

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

 more tumid than the S. striatinum. Quite rare. I have never 

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

 the late Prof. Adams, of Amherst. 



