432 THE CHICAGO ACADEMY OF SCIENCES. 



once thought to be a form of Galba contracta, but the above disposition 

 now appears to be the most logical. 



Canadensis is a distinct race of emarginata and will doubtless be 

 found to cover a wide range when it is sufficiently differentiated from 

 the other races of emarginata. The name emarginata has been made to 

 cover specimens of binneyi, catascopium, palustris and mighelsi, besides 

 several other forms, and has been quoted from Maine to Alaska. So 

 far as known no form of emarginata or its races, has been found west 

 of Minnesota or south of Michigan and Wisconsin. It is a type of 

 mollusk almost peculiar to the Great Lakes and the streams emptying 

 into them. It is also abundantly represented in the upper waters of 

 the Mississippi Valley drainage, in Wisconsin and Minnesota. The five 

 races recorded in the present monograph seem to be well characterized 

 representing five types of variation about each of which numerous 

 mutations have formed. 



Galba emarginata ontariensis ("Muhlfeldt" Kiister). Plate 

 XLV, figures 21-28. 



Limn&us ontariensis MUHLFELDT in Lit., KUSTER, in Chemn., eel. 2, p. 45, 

 1862. 



Limnaa emarginata var. A. ontariensis BINNEY, L. & F.-W. Sh. N. A., 

 II, p. 52, 1865. 



Limncea emarginata BAKER, Bull. Chi. Acad. Sci., II, pi. 1, fig. C, 1900. 



Limnaa catascopium WALKER, Nautilus, VII, p. 128, 1894 (part). 



SHELL: Ovate-conic, rather thick; periostracum light yellowish 

 horn or purplish white ; surface sculptures as in emarginata canadensis ; 

 there are from four to six rest varices on the shell ; nuclear whorls 

 as in canadensis; whorls 5^, the spire whorls flatly sloping, the body 

 whorl very convex ; spire short, broadly acutely conic ; sutures usually 

 not much impressed; aperture semi-oval, broadly rounded below and 

 much narrowed and angulated above, about as long as the spire; the 

 aperture is frequently much expanded appearing to flare markedly; 

 outer lip with an internal varix; inner lip broad, thick, closely ap- 

 pressed to the columellar region, completely closing the umbilicus ; the 

 parietal callus is usually well marked and is sometimes very heavy; 

 the inner lip is usually compressed at its junction with the parietal 

 wall forming a plait of variable distinctness ; axis twisted. 



Buffalo. 



u 



Fort Erie. 



a 



Saginaw Bay. 



