10 PLANORBIS CAMPANULATUS. 



GEOGRAPHICAL DISTRIBUTION. Inhabits New 

 England, New York, Ohio, Illinois, and the 

 Northwest Territory. 



OBSERVATIONS. 



Remarkable for the deflection and dilatation 

 of the extremity of the last whirl, the narrow- 

 ness of the aperture within; and in having the 

 later growths of the spiral but little larger, and 

 sometimes smaller, than in the preceding por- 

 tions. 



EXPLANATION OF PLATE 1. 



Figure 2 represents the animal in its normal position, 

 the shell being thrown to the left, and the tip of the apex 

 consequently downwards; and 1, the right, upper, obverse, 

 or umbilicated side; 4 is a view of the aperture, presenting 

 the penultimate whirl of a greater diameter than sometimes 

 occurs; 5 and 6 the distorted variety engonatus; 1 and 3 

 are taken from large shells, but I have found a single in- 

 dividual with a diameter of three-fourths of an inch. Figures 

 7 and 11 represent P. campanulatus, 8 and 10 being im- 

 mature. 



