Baktr — Notes on a Collection of Mollusks. 13 



Its chief characteristics are its bulbous, short, dome-shaped 

 spire and wide-spreading aperture. The specimens seem 

 adult, as the outer lip is thickened internally in several 

 specimens. 



A large, bulbous form of catascopiura is found in Lake 

 Superior (collection of J. H. Ferriss) but the individuals are 

 not constant, a lot of ten specimens showing every gradation 

 from typical catascopium to the rounded form. They are 

 also more fragile and the aperture does not spread in the 

 same manner as nasoni. Typical bulbous forms measure 

 13x9 ruill. Some catascopium from Pine Lake, Charlevoix, 

 Michigan, (collection Bryant Walker) have a rather short spire 

 but they are of a different shape ; the charlevoix specimens 

 are very variable. L. woodruffi Baker is differently shaped 

 and a typical figure is given for comparison. The types of 

 Nasoni are in the collection of the Chicago Academy of 

 Sciences and cotypes are in the collections of Dr. William 

 A. Nason and Mr. Bryant Walker. 



Lymnaea desidiosa Say. 



The specimens of desidiosa vary somewhat in size. The 

 localities and average lengths are as follows : 



Ox Bow, 6-8 mill. 



Whitefish Point, 10-11 mill. 



Long Lake, 10 mill. Very smooth shells. 



Sulphur Island. Varies toward variety modicella. 



Lymnaea g alb ana Say. 



Long Lake. 



Galbana is one of the most uniform of American Lymnaeas 

 and is a common shell from Maine to Michigan. Its wide 

 shell, short spire and somewhat rounded aperture will dis- 

 tinguish it from desidiosa and its varieties. 



