SPII^RIUM. 39 



The C. bulbosa, Anthony, is a little more globose than Mr. Con 

 rad s typical specimens, but presents no important characters of 

 difference. The shells of this species found in New Jersey and in 

 Illinois, are larger than those from Alabama. 



This species differs from most of our North American ones by 

 its full and very prominent beaks. 



7. Spliaerium rliomboideum, SAY. Animal, syphons reddish- 

 yellow. 



Shell subglobular, rhombic-orbicular, equilateral; ante 

 rior margin truncated ; posterior slightly angular ; basal Fig. 31. 

 nearly straight ; beaks full, but not prominent ; valves 

 slight, convex towards the beaks, gradually decreasing in 

 fulness towards the margins ; interior blue ; sulcations very 

 delicate ; epidermis olive-green, with often a straw-colored 

 zone on the margins ; young shell more compressed than the 

 adult ; hinge-margin nearly straight ; cardinal teeth rudi 

 mentary ; lateral teeth distinct, somewhat acute, not elongated. 

 Long. 0.50; Lat. 0.37; Diain. 0.31 inches. 



Hub. North Ainericn, in the States of Vermont, Connecticut, Massachu 

 setts, New York, Ohio, Michigan, and in Canada. (Cabinets of the Aca 

 demy of Natural Sciences of Philadelphia, Smithsonian Institution, Jay, 

 Prime, and others.) 



Cyclas rhomboidea, SAY, Acad. Nat. Sci. Phil. II II, 1822, 380. 



Cyclas cornea, var. 3, LAMARCK, An. s. vert. V, 1818, 558. 



Cyclas elegans, C. B. ADAMS, Bost. Jour. Ill, 1840, 330, pi. 3, f. 11. 



This, the most attractive species of Sphserium, is not easily 

 confounded with any other. Up to within a few years it was 

 usually known among collectors under the name of C elegans, 

 Adams. I have stated elsewhere 1 my reasons for considering the 

 C. elegans as identical with Say s shell. Though no longer rare 

 since 1851, when Mr. Whittemore found it in considerable abund 

 ance at one place near Cambridge, Mass., this species does not 

 seem to be very widely distributed ; it is confined to certain spe 

 cial localities. 



i Annals of the N. Y. Lyceum, vol. vi, 1853, 66. 



