6o Natural History Bulletin. 



Genus Cam-peloma. — /?«/". 



The moUusca of this genus i^MeJantho of authors) are ex- 

 ceedingly difficult to classify. Several species are recognized 

 but they are probably mere varieties of the same species. 

 The forms are so extremely variable that it is impossible to 

 satisfactorily separate them. 



Sinistral shells are frequently found. The following are 

 commonly recognized as species: 

 C. DECisuM. — Say. 



This is the most slender form, with relatively the longest 

 spire. Less common than the following, and usually found in 

 ponds or lakes. 

 C. SUBSOLIDUM. — Anth. 



Larger and heavier than the preceding, often reaching a 

 length of two inches. This frequently occurs in running 

 waters and is the most common form. 

 C. RUFUM. — Hald. 



Broader and with larger aperture than the preceding. It 

 is also usually thinner, and is frequently tinged with purplish- 

 red within the aperture and on the spire. It is rather rare, 

 though we found it in the Cedar river at Cedar Rapids in 

 considerable numbers m 1882. We consider these as mere 

 varieties of one species. 



Genus Lioplax. 

 L. SUBCARINATA. — Say. 



Rather common on muddy bottoms in quiet waters, espe- 

 cially along the Mississippi river. 



FAMILY— HELICINIDiE. 



Genus Helicina. 

 H. OCCULTA. — Say. 



This species is very peculiar in its distribution. It was 

 found in great abundance some years ago, under leaves on a 

 steep hillside facing north, near Iowa City by Mr. H. A. Pils- 

 bry and the writer in a tract less than two acres in area. The 



