The Mollusca of Eastern Iowa. 73 



S. sECURis. — Prime. 



Found quite commonly in ponds near Iowa Cit}-. Mr. L. 

 B. Elliott collected specimens probably of this species, in 

 Jasper County. 

 S. sPH^RicuM. — Anth. 



Found by Prof. Witter near Muscatine. 



S. TRUNCATUM. LiusL 



This species was found by us in considerable abundance 

 in a small pond near Iowa City. The pond is isolated and is 

 found at some distance from the river. Over 100 specimens 

 were taken in an area of less than twenty square feet. This, 

 as far as we know, is the only report of. its occurence in the 

 state. 



Three forms of Sphcermm distinct from the preceding have 

 been found by us, but in small sets, which render identification 

 very difficult. They may be new species but we reserve 

 them for future comparison and study. 



Genus Pist'dmm. — Pfr. 

 P. COMPRESSUM. — Pr. 



Found in a swamp southeast from Iowa City, and also 

 reported from Muscatine by Prof. Witter. 

 P. ABDITUM. — Haiti. 



Our most common species; found everywhere in rather 

 sluggish waters. A very large form which was found in a 

 small pond near Iowa City, and which was referred to this 

 species may be distinct. Our species of Pisidium call for 

 much more careful attention than has been given them thus 

 far. A Pisidium, species undetermined, was found b}' us in 

 the ^0-55 at Iowa City. 



ORDER— ASIPHO?^ I UA. 



FAMILY— UNIONID^. 



Gemis Unio. — Retz. 



U. ^sopus. — Green. 



Quite common in the larger streams. Very abundant on 



