North American Species of Petromyzontidw. 279 



XV. — A Review of the North American Species of 

 Petromyzontidce. 



BY DAVID S. JORDAN AND MORTON W. FORDICE. 



Read December 21, 1885. 



[ With an additional note on the Lamprey of Cayuga Lake. 



BY SETH E. MEEK.] 



In the present paper we have attempted to give the synonymy 

 of the Lampreys of North America, with analytical keys by 

 which the species may be distinguished. The specimens studied 

 belong to the Museum of the Indiana University, while numerous 

 others belonging to the United States National Museum have 

 also been examined. 



The North American species fall naturally into two groups, 

 which it seems most suitable to regard as genera ; although in 

 both groups there are large anadromous forms with strong denti-. 

 tion and small fluviatile forms with the teeth less specialized, — 

 modifications which may indicate subgenera. These genera may 

 be defined as follows : — 



ANALYSIS OF GENERA OF PETROMYZONTIDCE. 



a. Supraoral lamina (" maxillary tooth ") contracted, composed of two or 

 three cusps placed close together ; discal teeth numerous, in concen- 

 tric series ; anterior lingual tooth with a median depression or groove; 

 buccal disk large in adult (contracted in young). 



Petromtzon, 2. 



aa. Supraoral lamina very large, expanded laterally, forming a crescent - 

 shaped plate, with a cusp at either end, and sometimes a median 

 cusp ; anterior lingual teeth serrate more or less. 



Ammoccetes, 3. 



To these may be added a third genus, Bathtmyzon Gill, 

 which is said to differ from Petromyzon, in having "the suproral 



