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THE CHICAGO ACADEMY OF SCIENCES. 



pressed; whorls five and one-half to six, rounded, convex, 

 rather closely coiled; spire elevated, obtusely conical; aperture 

 forming a triangle, with rounded base, contracted behind the 

 peristome, which is thickened, roundly reflected, white, with a 

 small callosity near the umbilical region; the upper part of the 

 peristome is more reflected than the rest, so that in a front view 

 of the aperture this part presents a thin edge instead of a broad 

 curved surface; terminations widely separated, connected by a 

 very thin callus; umbilicus closed but the region indented; base 

 flatly rounded. 



Greater diameter, 18.50; lesser, 15.50; height, 12.00 mill. (12395.) 

 17.00; " 15.00; " 13.00 " (12395.) 



FIG. 24. 



Radula of POLYGYRA PENNSYLVANIA Green. (Original.) c, cen- 

 tral tooth; 1, first lateral; 9, second marginal; 16, 18, ninth and eleventh 

 marginals; 25, eighteenth marginal; J, jaw. 



Animal: With a long and narrow foot, 27.50 mill, long 

 and 4 mill, wide; color blackish or lead color on head, neck 

 and eye-peduncles lighter on base of foot; heart situated near 

 junction of peristome with body- wall; pulsations regular, 

 eighty-five per minute. 



Jaw: Arched, ends squarely truncated; anterior surface 

 armed with eleven wide, heavy ribs which denticulate the upper 

 and lower margins. The jaw is of the same width throughout 

 its length (Fig. 24, J). 



