64 NEW-YORK FAUNA — MOLLUSCA. 



Planorbis CORPULENTUS. 



PLATE VIII. FIG. 185.* a. b. 



Planorbis corpulentus. Say, Long's Exped. St. Peters, Vol. 2, p. 262, pi. 15, fig. 9. 

 P. id. Adams, American Journal of Science, Vol. 40, p. 2G9. 



Description. Shell large, dextral. Whorls three to four, rather rugged with coarse wrinkles. 

 Upper surface much flattened, and edged by an acute line, which is distinct to the margin of 

 the lip : sides hardly rounded, and terminated below by another carina not as sharp as the one 

 above. Spire slightly concave. Umbilicus exhibiting all the volutions to the apex. Aperture 

 longer than wide ; the upper part extending higher than the preceding volution, and the 

 lower part declining much lower than the lower line of the same volution. 



Color, olive brown. 



Diameter, 0-7. Height, 0"2. 



This animal is found in Lake Champlain, and in other portions of the State. There is 

 much diversity of opinion in relation to this species ; some supposing it to be an exuberant 

 growth of trivolvis, and others assert it to be a large variety of lentus. To me it appears to 

 want the nearly equal concavity of both the upper and under surfaces of the trivolvis, and 

 the appearance of all the volutions distinguishes it from lentus. 



It has been observed in Lake Champlain, and has a wide geographic range. The following 

 species, described by Dr. Gould, I have not seen myself; but as they exist in Massachusetts, 

 they will in all probability be found in this State. 



Planorbis hirsutus. 



Planorbis hirsutus. Gould, American Journ. of Science, Vol; 38, p/ 196.' 

 P. id. Id; Invertebrata of Mass: p. 206, pi. 135. 



Description. Shell small : both sides concave, the left rather more than the right, but the 

 concavity is there more limited by the presence of a subangular ridge on the outer whorl. 

 Whorls three ; the outer one rapidly increasing. Surface exhibiting traces of revolving lines 

 when denuded, but usually covered with a dark pigment or epidermis bristling with rigid hairs, 

 which are arranged in close revolving lines : lines of growth very faint. Aperture suboval, 

 oblique ; its diameter from side to side shortest. 



Color. Transparent brownish yellow. Animal slate-colored above on the head, with a 

 darker line along the tentacles ; foot chesnut. 



Diameter, 0-4. Height, 0-15. 



Stagnant pools. Allied to dejlectus. 



