56 THE NAUTILUS. 



more elevated and the acute apex is tipped with reddish-brown. 

 Axis straight, aperture ovate, smooth and shining surface, rarely 

 showing varicose bands. Color yellowish-white grading into a pale 

 yellowish chestnut in some forms. It usually has four whorls. 

 While white, it is not porcellaneous. Lea's description is correct. 



P. saffordi Lea, is a form of this species. 



Distribution : Along the Great Lakes. 



Physa integer Haldeman. 



Subspecies : Physa integer billingsi Heron. 



This is a very distinct species, described in 1841 from shells found 

 in Indiana. It is distinguished by its oval form, light color fre- 

 quently banded with white, deeply impressed sutures, ear-shaped 

 aperture and somewhat rough but shining surface. It is not closely 

 allied to any other species. It requires two seasons to reach matu- 

 rity. Diameter seven-tenths the length. 



It is the only species that extends from the Lakes to the Gulf. 

 It inhabits all the country bordering on the Lakes from Ontario 

 west, and extends south and west as far as San Antonio, Texas. I 

 have collected live forms in the latter place, and found it fossil in the 

 post-pliocene at Belton, Texas. 



Its distribution being different from that of any other species 

 raises a doubt as to the identity of the species at the extreme ends of 

 the territory covered. It has not been reported from south of the 

 Obio river, nor from eastern Arkansas, but seems to occupy a belt 

 lying between central Arkansas and central Kansas, continuing 

 about the same width to the Gulf. 



Physa billingsi Heron. The type was taken in Rideau river, near 

 Ottawa, Canada. The first examples sent me from that locality 

 varied so much from any described form that I was inclined to 

 accord it specific rank, but having received it from several localities 

 in Michigan, I am now placing it here as a well-marked variety. 



It is smaller than P. integer, of finer texture, and the sutures are 

 much less impressed. None of them have the ear-shaped aperture. 

 The lip is expanded and in many of them forms the arc of a circle. 

 In some of them the diameter is nearly as ereat as the length. From 

 this form the)' graduate into the usual form of P. integer. 



Its distribution, so far as known, is confined to Canada and 

 Michigan. 



