86 



THE NAUTILUS. 



gravel, sand, clay, and mud bottoms. Most abundant in mud 

 in 4-11 feet of water. The specimens are smaller than normal. 



Pisidium vesiculare Sterki. Mud bottom in water 8-11 feet 

 deep. 



A number of Pisidia and Musculia are still in the hands of 

 Dr. Sterki awaiting identification. They are either peculiar 

 forms of well known species or are undescribed, and several 

 species are represented. Of the material collected in 1915 Dr. 

 Sterki says; "You should have 30 species or more of Sphseriidae 

 in your vicinity; and there ought to be more than 20 species 

 (plus varieties) of Pisidium.'' 7 With the 1916 material we 

 nearly reach Sterki' s estimate of probabilities — 26 species of the 

 family named and six unnamed. Of Pisidium there are 18 

 named species and five unnamed. Several of the species listed 

 are recorded from New York State for the first time. The 

 Sphseriidae of Lower South Bay consist of small individuals with 

 slight shells and more or less weak hinges due to some physical 

 property of the water, perhaps a lack of lime. The maximum 

 development of this family, both in species and individuals, 

 appears to be in comparatively deep water. 



VlVIPARIDAE. 



Vivipara contectoides W. G. Binney. Collected from a mud 

 bottom in 9 feet of water. Only one specimen, half grown, 

 was found and this was probably brought to its location by cur- 

 rents. This species is abundant in the west end [of the lake, 

 near Brewerton, where it lives on a sand bottom in shallow 

 water. 



Campeloma decisum (Say. ) Collected from a sand and clay 

 bottom in water one and a half to 5 feet deep. More abundant 

 on a clay bottom. The majority of the individuals of decisum 

 collected in July 1916 were young or immature, adults being 

 very rare. It seems evident that the young of this species are 

 born in the spring and attain their first year's growth by Sep- 

 tember or early October. Information concerning the details 

 of the breeding habits of this group of mollusks are desirable. 



