12 FISHES OF ILLINOIS 



end of the plate larger than those (4 or S) between; 3 lateral (extraoral) 

 bicuspids on each side of mouth; remaining teeth simple, unicuspid, and 

 rather weakly developed* Dorsal fin consisting of an anterior and 

 posterior portion, separated in adults by a deep notch (in breeding sea- 

 son) or divided by a narrow space; in larvas 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 Michigan 

 '(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 col- 

 lections is probably a consequence of its small size and non-para- 

 sitic 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. 



