164 College of Forestry 



of New York. It -is an interesting case of bathy metrical dis- 

 tribution that z'ernwiiianum should occur at all depths exam- 

 ined but that solidulum and sulcatum should be found only at 

 8 feet and deeper. The last species was obtained only between 

 8 and 13 feet. 



Genus Musculium Link 



19. Musculium securis (Prime). Not collected in 1916. 



20. Musculium rosaceum (Prime). Not collected in 1916. 

 *2i. Musculium truncatum (Linsley). 



Found only in one habitat, on a clay bottom in four feet of 

 water. 



*22. Musculium transversum (Say). 



This common species occurred in four habitats, on a sand 

 and clay bottom, in water one and a half to four feet deep. 

 It is, like some of Sphccrium, of smaller size than is normal for 

 the species. 



*23. Musculium species. 



A number of specimens occurred in many habitats which 

 somewhat resemble securis. These are thought by Dr. Sterki 

 to possibly represent an undescribed species. It was found in 

 water one and a half to 8 feet deep, on gravel, sand, clay, and 

 mud bottom. 



Genus Pisidium Pfeiffer 

 *24. Pisidium abditum Haldeman. 



Specimens of this species, or of a form very closely related 

 to it, were found on sand, clay, and mud bottoms, in one and 

 a half to 8 feet of water. They were small and not charac- 

 teristic. 



*25. Pisidium adamsi affine Sterki. 



Collected in one habitat on a gravel bottom in three feet of 

 water. 



26. Pisidium aequilaterale Prime. Not collected in 1916. 



