312 THE CHICAGO ACADEMY OF SCIENCES. 



upper part, more than a half and less than two-thirds the length 

 the entire shell; peristome thin, thickened on the inside by a 

 callus which is either bordered by a dark chestnut band or else 

 is itself of that color; columella thickened with a decided 

 white callus or plait; the lower part of the aperture is produced; 

 the periods of winter hibernation are frequently marked by a 

 whitish band in the body of the shell; protoconch consisting 

 of a trifle more than one smooth, rounded, dark chestnut-col- 

 ored whorls. 



Length, 17.00; width, 9.00; aperture length, 11.00; width, 4.50 mill. (9331.) 



" 26.00; " 12.00; " 14.00; " 5.50 " (8493.) 



" 24.00; " 11.50; " " 13.00; " 5.00 " (8493.) 



" 19.00; " 10.00; " " 12.00; " 5.00 " (8493.) 



" 22.00; " 10.00; " " 12.50; " 5.00 " (8471.) 



Animal: With a long, rather narrow foot, acutely pointed 

 behind and rounded before, where it is produced into two lateral 



FIG. 110. 

 Animal of PHYSA GYRINA Say. (Original.) 



lobes (vela); the foot does not extend much beyond the edge 

 of the shell, color blackish or yellowish gray, dotted or flecked 

 with whitish or yellowish, the dots being distinctly seen through 

 the transparent shell; the front of the head is .ornamented 

 with two yellowish spots of good size, composed of numerous 

 minute dots; the mantle is brown, spotted with yellowish, is 

 reflected over a portion of the shell on the right side and pro- 

 duced into 4-10 filiform digitations arranged in two series 

 apical and columella; tentacles very long and slender, taper, 

 ing to a point; head distinct, separated from the foot by a 

 short neck; mouth large, in the lower plane of the head, show- 

 ing plainly the jaw and radula while the animal is grazing 

 along the side of an aqiiarium; eyes placed on swellings at the 

 inner base of the tentacles; respiratory cavity on left side of 

 shell at the lower .point where the peristome meets the body 

 whorl. Length of foot, 15.00 mill.; width, 4.00 mill. (Fig. 1 10). 

 Jaw: In one piece, arched, striated, provided with a cen- 



