224 ~  NEW-YORK FAUNA — MOLLUSCA. 
Color. Young, light waxen, passing into greenish horn in the adult, with bluish white or 
yellowish white on the margin. Animal, light pink. 
Vertical axis, 0°3 —- 0°45; transverse ditto, 0°45 — 0°6. 
This species is common in swamps and sluggish streams in every part of the State. Its 
hitherto ascertained geographical range is from Masssachusetts to Ohio. I agree in opinion 
with Dr. Gould, that the varieties 2 and 3 of the Cycla de cornée accord perfectly with our 
species. 
CycLAS RHOMBOIDEA. 
PLATE XXV. FIG. 263. 
(STATE COLLECTION.) 
Cyclas rhomboidea. Say, Jour. Acad. Nat. Sciences, Vol. 2, p. 380. 
Cc. id. Apams, Am. Jour. Sciences, Vol. 40, p. 277. 
Description. Shell solid, transversely elongated, subequilateral, rhombiform ; the basal 
margin regularly curved, approaching a straight line. Beaks not greatly elevated, contiguous, 
often decorticated. Anterior margin subtruncated ; the posterior margin obtusely rounded. 
Two cardinal teeth in each valve, oblique with an intermediate pit; the anterior smallest : 
the lateral teeth distinct, bipartite at each extremity. Surface polished, with minute concen- 
tric striz : cavity with faint impressed incremental strie. 
Color. Epidermis olive-green to light chesnut ; within opake white. 
Vertical axis, 0°45; transverse ditto, 0°7. 
I refer to this species specimens procured from Rockland county by Dr. Budd, and from 
Lake Champlain. They are remarkable for their polished surface and rhomboidal outline. 
The dimensions given above are larger than those of Mr. Say. 
CYcLAS ELEGANS. 
Cyclas elegans. Apams, Am. Jour. Vol. 40, p. 277. Ip. Bost. Jour. Vol. 3, p, 330, pl. 3, fig. 11. 
Cc. id. Gou tp, Invertebrata of Mass. p. 74, fig. 55, 
Description. Shell rhombic-orbicular, compressed in the young, much inflated in the adult ; 
the extremities subtruncated, so as to appear rhomboidal. Beaks nearly central, not promi- 
nent. Surface with fine concentric strie ; the valves not regularly convex, but somewhat 
flattened down the middle, so as to produce a slight elevation from the beaks to the anterior 
and posterior portions of the basal margins. Cardinal teeth rudimentary, very thin; lateral 
teeth strongly developed. Basal margin nearly straight. = 
Color. Epidermis olive-green, with a straw-colored marginal zone, and narrow zones at 
the different stages of growth; within bluish white. 
Vertical axis, 0°35; transverse ditto, 0°5. 
