Description of New Species of Pisidium. 65 



Remarks.— A. rare shell ; more inflated and heavier than either 

 P. compressum or P. altile. 



2. Pisidium contortum. 



CABINET OF THE NEW YORK LYCEUM OF NATURAL HISTORY. 



Plate I. Fig. 2, a, b, c. 



Shell small, elongated ; beaks large and prominent ; anterior 

 margin very abrupt, posterior one less so ; slight ridges from the 

 beak towards the inferior part of the anterior margin. Sulca- 

 tions slight. Length 0.13, Breadth 0.07, Diam. 5 inches. 



Habitat— Found subfossil at Pittsfield, Mass., in company 

 with P. ventricosum. (Shurtleff.) 



Remarks.— This is a singular species, unlike any other of this 

 country. Its foreign analogue is the P. sinuatum of Bourgui- 

 gnat. See Petit's Jour, for 1852, page 49. 



3. Pisidium TCoYeboracense. 



CABINET OF THE NEW YORK LYCEUM OF NATURAL HISTORY. 



Plate I. Fig. 3, a, b. e. 



Shell large, high, not much elongated, full ; beaks prominent 

 and large ; anterior margin elongated, posterior one curved. 

 Sulcations not very light. Color varying from greenish-yellow 

 to brown. Interior light blue. Length 0.35, Breadth 0.18. 

 Diam. 0.13 inches. 



Habitat— Washington County, N. Y. (Ingalls), and Herki- 

 mer County, N. Y. (Lewis). 



Remarks.— This is one of our largest American species. Com- 



