102 



CYCLADID^. 



Cyclas sunllis, Say, Nicholson's Encyc. 1st Amer. eel. ii. pi. 1, fig. 9 (1816). — Be Kay, 

 Nat. Hist. New York, 222, pi. 25, figs. 264, 263 —Lewis, Proc. Bost. Soc. Nat. 

 Hist. V. 122; vi. 2. — Also Jay, Adams, Linsley, and Mighels. 



Cyclas sulcata, Lam. An. sans Vert. v. 560 (1818), 2d cd. vi. 271. — Delessert, Receuil, 

 pi. 7, fig. 3. — Stimpsox, N. E. Mollusks, 16. 



Cyclas Suriuto(/ea, Lam. An. sans Vert. v. 560 (1818); 2d ed. vi. 271. — Delessert, 

 lieccuil, j>l. 7, fig. 9. 



Cyclas f/ii/aiitca and pomlcrosa, Prime, Proc. Bo-^t. Soc. Nat. Hist. iv. 157 (1851). 



Sphoiriuiii sulcatum, Prime, Pr. Ac. Nat. Sc. xi. 299 (1860) ; xii. 403. 



Cyclas rhomhoidea, De Kay, Nat. Hist. New York, 224, pi. 25, fig. 263 (1842). — C. B. 

 Adams, in Thonips. Verm. 168. — Stimpson, Shells of New England, 16. — Lins- 

 ley, Sillini. Journ. xlviii. 276. 



For full synonymy see Prime's Synonymy of Cyclades, in Proc. Acad. Nat. Sc. xi. 299. 



Shell sub-oval, nearly equipartite, varying much in its outline. 

 In the adult shell the extremities are Ijroadly and nearly equally 

 rounded, the posterior part being somewhat the longest and most 



pointed, the base very little curved ; 

 valves very convex, remarkably broad 

 across the beaks, which are Init slightly 

 elevated ; color dark chestnut-brow^n, 

 within bluish. The young shell is thin 

 and compressed, the hinge-margin nearly 

 a straight line, the extremities truncated 

 so as to give the shell a quadrilateral 



form ; and the color is 



a light lemon- 



S. simile. Enlarged. 



color, or honey-yellow. The interme- 

 diate specimens exhibit all the grada- 

 tions of shape or color between the old and young. Surface at 

 every stage regularly wrinkled concentrically, with strongly raised, 

 sharp lines of growth, and generally a more conspicuous wave mark- 

 ing the former year's growth of the shell; beaks usually eroded. 

 Hinge with minute, very oblique, cardinal teeth, the marginal ones 

 distinct, strong, and white. Length, seven tenths of an inch; 

 height, half an inch ; Ijreadth, two fifths of an inch. 



Found in the larger ponds and rivers, especially along the muddy 

 banks of the Connecticut. New England and Northern States. 

 Lachine Canal, Metis Lake {Be/l) ; Truro, Nova Scotia (^3Ic Cul- 

 loch'). 



This species is closely allied to the C. rivicola of Europe in shape 

 and size ; its raised concentric striae, however, a|)pear to be much 

 more prominent. It may always be distinguished l)y tliese conspic- 

 uously raised lines, for they are exhibited by no other American 

 species in so great a degree. Several other species are described 



