54 THE NAUTILUS. 



overlook an individual varying in the above respect. It will be well 

 for collectors to keep their eyes open for such abnormal individuals ; 

 it may be found that they occnr oftener than is supposed. 



R. E. C. STEARNS. 

 Los Angeles, May 2, 1901. 



THE AMERICAN PHYS.E. 



BY O. A. CRANDALL, SEDALIA, MO. 



Physa gyrina var. albofilata Ancey. This variety is confined to 

 southwest Missouri and northwestern Arkansas, extending into the 

 Indian Territory and Kansas. It is distinguished by its lighter 

 color, fine lines of growth, rarely showing cross strise, generally 

 malleated on some part of the surface, and large white varicose bands. 

 It is generally found with five whorls. 



Forms : Physa hawni Lea, P. cylindrica Newcomb, Physa smith- 

 soniana Lea. 



P. gyrina is the most widely distributed of all the American species. 

 It extends over all the territory between the Alleghanies and Rocky 

 Mountains, and from the Arctic region south into Alabama and 

 Texas. I have examples from near Philadelphia, Pa., and from 

 Routt county, Colorado, but I do not consider them permanent in- 

 habitants of those localities. It is possible that they may yet be 

 found to extend as far west as the Sierra Nevada Mountains, but I 

 have been unable to obtain any evidence that they now inhabit the 

 Great Basin. I account for their being found outside of the limits 

 here given by the ova being carried on the feet of migratory birds, 

 by means of which isolated colonies are planted, which survive for a 

 time, but finally become absorbed by the more numerous inhabitants 

 and disappear. They may be called sporadic colonies. This also in 

 part accounts for the hybridization that has produced so many forms 

 that have been described as new species, only to vanish in a season. 



Physa elliptic;! Lea. 



Includes the sub-species Physa elh'ptica troostiana Lea, Physa ellip- 

 tica minor n. v. 



There probably is not a more distinct species in the genus than 

 this, yet Binney and Haldeman place it in the synonymy of P. 

 gyrina Say. Tryon recognized it as a species, gave it a very large 



