SrH.ERIUM. 103 



as having them, such as arc named under the synonymes ; Init they 

 are probably all of them varieties of this species. The young, dif- 

 fering widely as it docs from the adult, has been commonly received 

 in our cabinets as Say's C. rhomboidea. A specimen one fourth of 

 an inch long would answer very well to his description. What the 

 true rhomboidea is, I have not yet been able to satisfy myself. The 

 two species of Lamarck, also, I believe to be varieties of this shell ; 

 and very probably his C. striatina also. 



[Mr, Prime, by an examination of si)cciniens in the Jardin des 

 Plantes, has come to the conclusion, no doul)t correctly, that this 

 is certainly C. sulcata of Lamarck, and has given that as the prior 

 name. lie seems not to have seen the lirst edition of Nicholson's 

 Encyclopaedia, in which Say gave his description, which bears date 

 two years earlier (181(3).* C. Sarrafofrea, however, represents the 

 adult shell, according to Delessert's figures, and C. sulcata and 

 striatina, young forms. 



Sphserium partumeium. 



Fig. 54. 



Shell rounded-oval, sub-equipartite, lowest anteriorly, somewhat angular be- 

 hind ; tliin and fragile ; valves very convex, minutely wrinkled by lines of growth, 

 and obsoletely radiated ; light horn-color ; beaks elevated. 



Cyclas partnmcia, Say, Jouvn. Acad. Nat Sc. ii. .'iSO (1822). —Ferussac, Mag. de Zool. 



183.5. — T)E Kay, Nat. Hist. New York, 22.3, pi. 25, fig. 202. — Stimpson, Shells of 



New England, 16. — Puimio, rroe. Bost. Sec. Nat. Hist. iv. 165,278. — Mighels, 



Shells of Maine, 12, in Journ. Bost. Soc. Nat. Hist. iv. 318. 

 Cyclas cornea, var. 2, Lam. An. ,sans Vert. vi. 2G8 (1835). — C. B. Adams, in Thonip. 



Verm. 168. — Gould, Inv. 1st ed. 73 ; Catal. .30. 

 Cijclus carulea, Prime, Proc. Bost. Soc. iv. 161 (1852). 

 Cyclas miraliilis, Prime, ibid. iv. 167 (1852). 

 S/ihcerium cmrutenm and minibile, Prime, Adams's fien. ii. 450. 

 Spharium partumeium, Prime, Pr. Ac. Nat. Sc. xi. 296 (1860). 

 Sphcerium partumhun. Prime, Op. cit. xii. 29. 



See Prime's Synonymy of C}clades, in Proc. Acad, of Sciences, xi. 296. 



Shell rounded-oval, highest behind, thin, fragile, pellucid, some- 

 what inflated ; beaks nearly central, moderately elevated, inclining 

 inwards ; hinge-margin nearly straight, passing by a regular curve 

 into the rounded anterior extremity, but curving suddenly l)ehind, 



* Dr. Gould is incorrect in regard to the date. The second volume of the first edition, 

 containing Mr. Sav's article Conchology, hears the date of 1817. The only public library 

 which to my knowdedge contains this edition is that of the U. S. Naval Academy at An- 

 napolis. — W. G. B. 



