FAMILY CYCLAL\« CYCLAS. 223 



central ; a lamelliform plate in the place of cardinal teeth ; lateral teeth scarcely rising above 

 the margin of the shell ; cavity chalky within, with faint radiating furrows. Color, dark 

 olive brown. Vertical axis, 0-5 ; transverse ditto, 0-6. It was obtained from Sandy creek, 

 Orleans county, and I had but a single specimen. 



Cyclas dubia. 



plate xxv. fig. 261. 



(STATE COLLECTION.) 



Cydas dubia. Say, Nich. Ency. Ed. Am. Vol. 4, pi. 1,-fig. 10. 

 C. strialina. Lam. An. sans vert. EJ. Brux. Vol. 2, p. 388. 

 C dubia. Gould, Invertebrata of Mass. p 75, ftg. 5G. 



Description. Shell small, moderately solid, subtriangular, oblique, subovale, convex ; the 

 beaks not very prominent, placed much nearer one end. Surface with minute concentric 

 ridges, which become more distinct towards the basal margin. Primary teeth very distinct, 

 placed between two pits in one valve, and two divaricating ones in the other ; the exterior 

 lamellar tooth very small, with the fossa; acutely elliptical. 



Color. Epidermis olive-green tinged with reddish, with occasionally darker bands marking 

 the stages of growth. 



Vertical a.xis, 0-25 - 0-3 ; transverse ditto, 0-3 - 0-35. 



I have obtained specimens of this shell from Herkimer county, and Dr. Newcomb has no- 

 ticed them at Palmyra, Wayne county ; they are doubtless to be found in ponds and ditches 

 in every part of the State. The description of C. striatina by Lamarck, which he procured 

 from Lake George, applies in every particular to this species. 



Cyclas partumeia. 



PLATE XX v. FIG. 262. 



(STATE COLLECTION.) 



Cyclas partumeia. Say, Jour. Acad. Nat. Sciences, Vol. 2, p. 380. 

 Cyclas cornea, var. 2, 3. Lamarck, An. sans vert. Ed. Brux. Vol. 2, p. 388. 

 C. partumeia. Adams, Am, Jour. Sciences, Vol. 40, p. 279. 

 C id. Gould, Invertebrata of Mass. p. 73, fig. 54. 



Description. Shell thin, fragile, pellucid, inflated, rounded oval. Beaks nearly central and 

 moderately prominent. Posterior margin more broadly rounded than in front ; basal margin 

 regularly curved. Surface glossy, with minute regular concentric wrinkles and larger undu- 

 lations which arc impressed within ; under the lens, faint radiating lines may be detected. 

 Hinge teeth prominent and diverging ; lateral teeth strong and prominent. 



