SPILERIUM. 105 



Cydas elegans, AnAMS, Bost. Jonrn. Nat. Hist. iii. 3.-30, pi. 3, fig. 11 (1840) ; in Thomp- 

 son's Nat. Hist. Vermont, 163. — Gould, Inv. Mass. 74, tig. .55. — De K.w, Nat. 

 Hist. New York, 224. — C. B. Adams, Sliells of Vermont, 30. — Stimpson, Shells 

 of New England, 16. —Prime, Proc. Bost. Soc. iv. 16.5. 



Ciiclas cornea, var. 3, Lam. An. sans Vert. 2d cd. vi. 268. 



Shell ill its younger stages compressed, in an adult state tumid, 

 sub-globular, the extremities truncated or terminating abruptly, so 

 as to appear somewhat four-sided or rhomboidal ; beaks not prom- 

 inent, the anterior side a very little the shortest and nar- 

 rowest ; basal margin nearly straight and parallel to the 

 upper margin ; the valves are not regularly convex, but 



somewhat flattened down the middle, so as to exhibit an 



obtusely rounded ridge passing from the beaks towards ^ rhomboi- 

 each lower angle; surface delicately marked with fine, E^ia,!^ed. 

 rounded, concentric wrinkles; color olive-green, with a 

 straw-colored margin, and narrower zones at each stage of growth. 

 Hinge rather strong, the cardinal teeth rudimentary, the lateral 

 ones large and strong. Interior bluish. Length, nearly one half 

 an inch ; height, seven twentieths of an inch ; breadth, eleven for- 

 tieths of an inch. 



Found in a ditch running through the Camljridge meadows, near 

 Fresh Pond. Vermont, Connecticut, New York, Ohio {Prime}. 



This is a remarkable and beautiful species, and seems to be rather 

 rare. Excepting the above locality, I know of no other but at Wcy- 

 bridge, Vermont, whence it was sent me l)y Prof. Adams. It is 

 about the size and width of <S. partumeium, but is a very much thicker 

 shell, differently colored and sculptured, and its four-sided, angular 

 outline is quite different. The young of S. simile, though equally 

 four-sided, is much longer proportionally, the color much darker, 

 and the ridges on the surface much coarser. In this species the 

 foiu' sides are nearly equal. 



[Mr. Prime after much investigation, and finding it to answer to 

 all the terms of Say's description, concludes the above species to be 

 the long-sought-for C. rhomboidea, and in this conclusion I concur. 



Sphaerium Verraontanum. 



Shell very oljliquo and tumid, anterior margin very abrupt. 



Sphreriiim Vermontana, Prime, Proc. Ac. Nat. Sc. xii. 128 (1861). 

 SpJuerium Vermontanum, Prime, Proc. Ac. Nat. Sc. xii. 408 (1861). 



Shell very oblique, tumid, inequilateral, full ; anterior margin 

 abrupt, posterior drawn out to an angle, basal slightly curved ; 



