NATURAL SCIENCES OF PHILADELPHIA. 99 



clay banks in the Mohawk Paver, preferring swift water. I have 

 no doubt a variety of this species furnished the type of Mr. Tryon's 

 Gon. Haldemani. 



Goniobasis virginica, Gmelin. 



Common enough in the canal at long intervals. Has no doubt 

 been introduced since 1856. Is said to abound in the Hudson 

 River, and in streams near Buffalo. Is very seldom found in the 

 Mohawk River. 



In 1871 I found specimens which attain nearly the size of adults 

 of this species, but which exhibit colors and forms somewhat 

 unlike it. They seem to blend the colors of Trypanosoma sub- 

 ulare and Goniobasis livescens, and approximate the form and 

 size of Gon. virginica. I am persuaded by the circumstances 

 attending them that they are hybrids, and probably derived from 

 Gon. virginica, and perhaps both the other two mollusca just 

 named. The supposed hybrids are not found apart from virginica. 

 Feeling unwilling to assume the responsibility of suggesting hy- 

 bridity in a case which others might have settled by proposing a 

 new species, I submitted specimens to Mr. Charles M. Wheatley 

 for his opinion. I feel privileged to say that Mr. Wheatley assents 

 to my view respecting the shells. 



Helix albolabris, Say. 



A common species. A variety with a tooth is found in the 

 town of Litchfield. A single reversed specimen was found near 

 Mohawk in June, 1811. 

 Helix alternata, Say. 



This is the most abundant Helix of this region. It does not 

 offer any notable varieties. 



Helix arborea, Say. 



Formerly somewhat abundant, but now extremely rare in the 

 valley of the Mohawk. 

 Helix chersina, Say. 



Damp grounds along the valley of the Mohawk. This species 

 is rare, and very few have been seen for many years. 

 Helix concava, Say. 



Somewhat abundant in damp ravines. 

 Helix dentifera, Binney. 



Found in ravines in the town of Litchfield (1871). Only a very 

 1872.] 



