70 NORTHERN FISHES 



the University of Minnesota collections from Lake Pepin are of this 

 species. 



Its habits are similar to those of the silver lamprey. 



GENUS Entosphenus Gill 



Members of this genus have the dorsal fin broken into two parts 

 and separated from the caudal fin. Only one species of this genus 

 occurs in the Upper Mississippi Valley. 



AMERICAN BROOK LAMPREY 



Entosphenus laniottenii (LeSueur) 



The brook lamprey (Figure 2) is small and very slender, seldom reach- 

 ing a length of over 8 inches. The funnellike buccal cavity is small, the 

 diameter being only slightly more than that of the body. Most of the 

 teeth are blunt and small; three large bicuspid teeth are located on 

 each side of the mouth. The intestine of the adult is degenerate and 

 nonfunctional. The dorsal fin of the adult consists of an anterior and 

 posterior portion separated by a slight notch, or narrow space. 



Figure 2. American brook lamprey, Entosphenus lamottenii, 6 inches long. 



The brook lamprey ranges northward from Tennessee and Missouri 

 to western Pennsylvania and through the Great Lakes drainage to 

 northern Minnesota. It occurs also in the Atlantic drainage from the 

 Connecticut River to Maryland. It is widely distributed in Minnesota 

 and neighboring states. Surber (1920) reported it from the south 

 branch of the Whitewater River at Elba, Minnesota. An ammocoete 

 provisionally assigned to this species is in the University of Minnesota 

 collections from the Sturgeon River in the Arctic drainage in St. Louis 

 County. The brook lamprey is present in many of the tributaries of 

 the St. Croix River and is very abundant in many of the smaller 

 tributaries of the Minnesota River near Minneapolis. Greene (1935) 

 reported it from a number of small streams in Wisconsin. 



The brook lamprey is confined to small, clear streams, where they 

 are often very numerous. However, the ammocoetes are usually hid- 

 den in the mud, and so only the adults, during their brief spawning 

 period, are observed. In the Credit River, a small tributary of the 



