S. rhnmboi- 



iltiiin. 

 Eiilarsed. 



SPH.ERIUM. 105 



. Cydas elegans, Adams, Bost. Journ. Nat. Hist. iii. .330, pi. .3, fig. 11 (1840); in Thomp- 

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

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

 of New England, 16. — Prime, Proc. Bost. Soc. iv. 165. 

 Cydas cornea, var. 3, Lam. An. sans Vert. 2d cd. vi. 208. 



Shell ill its youiig-cr stages compressed, in an adult state tumid, 

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

 as to appear somewhat four-sided or rhomboidal ; Ijcaks not i)rom- 

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

 rowest ; basal margin nearly straight and parallel to the 

 iij)per margin ; the valves are not regularly convex, but 

 somewhat flattened down the middle, so as to exhibit an 

 olitusely rounded ridge passing from the beaks towards 

 each lower angle ; surface delicately marked with line, 

 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 ])luish. Length, nearly one half 

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

 tieths of an inch. 



Found ill a ditch running through the Cain))ridge meadows, near 

 Fresh Pond. Vermont, Connecticut, New York, Ohio {Prime'). 



This is a reinarkal)le and beautiful species, and seems to be rather 

 rare. Excepting the abcne locality, 1 know of no other h\xt at Wey- 

 bridge, Vermont, whence it was sent me by Prof. Adams. It is 

 al)out the size and width of S. parfiiinriiun, but is a very much thicker 

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

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

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

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

 four 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. 



SphsBrium Vermontanum. 



Shell very oljli((ne and tumid, anterior margin very abrupt. 



Splutriura Vmnontana, Prime, Proc. Ac. Nat. Sc. xii. 128 (1861). 

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



Shell very oljli(|ue, tumid, inequilateral, full ; anterior margin 

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



