308 MEMOIRS OF THE CARNEGIE MUSEUM. 



Soft parts identical with those of L. ovata and L. ovata ventricosa. Glochidia 

 not observed. 



Breeding season: Gravid females have been seen only on Maj'^ 21 and 22, 1909. 

 Most of my specimens were collected in the month of July, and no gravid females 

 were among them. Thus the interim seems to be in this month. 



Remarks: Simpson (1914) calls this form var. lurida (of ventricosa), and 

 believes that U . canadensis Lea is a synonym of ventricosa. However, I follow 

 Walker (1913) in considering the lake-form to be L. canadensis. 



This form has the same relation to L. ovata ventricosa, as has L. luteola rosacea 

 to L. luteola. It is a small, stunted, light-colored lake-form, which under certain 

 conditions shows the same tendency to become brownish near the beaks. The 

 shell is very variable in color. Specimens from the surf-beaten beaches are very 

 light in color, pale yellow; while those from protected locations in Presque Isle 

 Bay are darker, and tend to have more or less chestnut color toward the beaks. 

 The rays also vary greatly, and often are entirely absent. 



Old shells frequently show a peculiar variation in shape, not found in L. 

 ovata ventricosa, having a tendency to become more elongated. In this form the 

 growth-rests are also often more regular and more distinct than in ventricosa, but 

 this is not always the case. This character is best exhibited in specimens from 

 deep water, and less so in specimens from the surf. The specimens from Ottawa 

 River do not show this. They are also darker grayish green than the average 

 specimens from Lake Erie. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Lake Eric, Presque Isle Bay, and outer beach of Presque Isle, Erie; beach at Miles Grove, Erie Co. 



Other localities represented in the Carnegie Museum: 



Ottawa River, Ontario, Canada (B. Walker, donor). 



Lake Erie, Vermilion, (C. Goodrich), and Cedar Point, Erie Co., Ohio (C. Brookover; 0. E. Jennings); 



La Plaisance Bay, Monroe Co., Michigan (C. Goodrich); Port Rowan and Port Dover, Norfolk 



Co., and Port Colborne, Welland Co., Ontario, Canada (C. Goodrich). 

 Lake Huron, Saginaw Bay, Charity Island, IMicliigan (C. Goodrich). 



Distribution and Ecology (See fig. 32) : Type locality, St. Lawrence River, 

 Montreal, Canada (Lea). 



Besides the St. Lawrence, this form is found in Ottawa River, and very likely 

 at other localities in the lower St. Lawrence basin and Lake Ontario, generally 

 credited to L. ventricosa (Marshall, 1895; Whiteaves, 1863; Bell, 1859). It is 



