104 PROCEEDINGS OP THE ACADEMY OF 



Pisidium aequilaterale, Prime. 



Ditches and Erie Canal. Sometimes plenty. 

 Pisidium compressum, Prime. 



Erie Canal and Mohawk River ; also lakes and ponds. 

 Pisidium ventricosum, Prime. 



The shells of this region are between ventricosum and subrotun- 

 datum, Prime. I am inclined to believe subrotundatum is a small 

 variety of ventricosum. My local specimens were obtained from 

 a stagnant pool near Mohawk, and from Little Lakes. 



Pisidium virginicum, Bgt. 



Erie Canal and Mohawk River. 

 Pupa contracta, Say. 



Damp flat lands, Mohawk Valley. 

 Pupa pentodon, Say. 



Damp flat lands, Mohawk Valley. 



Somatogyrus subglobosus, Say. 



Erie Canal. Introduced since 1860. This species comes from 

 the west, and in a very few years has become numerically more 

 abundant than any other mollusc in the canal. 



Sphaerium croceum, Lewis. 



I described this species many years ago. Mr. Prime puts it in 

 the synonyms of one of his species (S. secure). Since the publi- 

 cation of Mr. Prime's papers I have had opportunity to study S. 

 croceum, and find it in very different circumstances from those 

 which determine the habits of S. secure, typical specimens of which 

 I have collected in Massachusetts. My shells are found usually 

 in coarse angular gravel anchored by a byssus. They are more 

 abundant in a small stream that connects the two " Little Lakes" 

 in the south part of this county than elsewhere. 



Sphaerium fabale, Prime. 



Small stream in the town of Litchfield, Herkimer County (head- 

 waters of the Unadilla River). Found in the fall of 1871. Brought 

 to notice by Dr. Litchfield. 



Sphaerium occidentale, Prime. 



Stagnant waters, subject to drying. Not unusually found alive 

 in the soil of dried stations. 



[July 16, 



