12 FISHES OF ILLINOIS 



weakly developed.* Dorsal fin consisting of an anterior and posterior 

 portion, separated in adults by a deep notch (in breeding season) or divided 

 by a narrow space; in larvae the fin divided by a space equal to the greatest 

 height of the fin; first dorsal about half the height of second. 



Males with a long urogenital papilla, whose length in breeding season 

 is equal to the diameter of the eye. 



Here described from 5 specimens, one from Lake Mich- 

 igan (presented by Dr. Jordan), and four from Cayuga Lake, 

 New York (from Dr. Gage). A half dozen larvae received from 

 an unknown source in the winter of 1903, probably from within 

 Illinois and in answer to circular letters of inquiry concerning 

 lampreys, are doubtless of this species. Its almost total absence 

 from our collections is probably a consequence of its small size 

 and non-parasitic habit. 



This species is known from western New York and the 

 Great Lakes to the Ohio and Mississippi rivers and west to Iowa 

 and Kansas. 



* It is the belief of Gage ('93) and others that this lamprey is not parasitic in habit. 



