26 



VERTEBRATE ANIMALS OF THE UNITED STATES 



to 4 (usually 2) approximated cusps; buccal funnel, when expanded, 

 much wider than the body, and with a double row of marginal fringes: 

 valleys of the Great Lakes and St. Lawrence River; southward and 

 westward into the Ohio, Missouri and upper Mississippi valleys; 

 common. 



/. unicolor (DeKay) (Fig. 10). Length 150 mm.; supraoral lamina 

 with 2 separated cusps; buccal funnel, when expanded, not wider than 

 the body, and with weak or obsolescent teeth; intestine degenerate 

 in the adult: basin of the Great Lakes; often abundant. 



2. Petromyzon L. Marine and fresh water lampreys with 2 sepa- 

 rated dorsal fins: several species, i in the United States. 



P. marinus h. Lamprey eel; great sea lamprey (Fig. 11). Length 

 up to 1,000 mm.; color blackish, more or less mottled; buccal funnel 

 large, with strong, pointed teeth, the innermost lateral teeth being 



^^^^^J0 



Fig. II. — Petromyzon marinus {from Jordan's Guide to the Study of Fiskes). 



enlarged and usually bicuspid; supraoral lamina with 2 approxi- 

 mated cusps; infraoral lamina with 7 to 9 strong cusps; muscle segments 

 between gills and anus about 70: North Atlantic along the American, 

 European and African coasts; southward to Florida, ascending the 

 streams to breed; common in the interior lakes of New York and 

 Lake Ontario. 



3. Entosphenus Gill. Marine and fresh water lampreys with 2 

 separate dorsal fins; teeth in groups, there being a marginal series 

 bordering the edge of the buccal disc, several enlarged teeth on each 

 lateral border of the mouth, a group on the anterior and one on the 

 posterior part of the disc: 3 species, i in Mexico. 



E. tridentatus (Gairdner). Length 450 mm. or more; color dark 

 brown; 4 enlarged lateral teeth on a side, the first and last bicuspid, the 

 middle two tricuspid; infraoral lamina with 4 to 6 cusps; supraoral 

 lamina tricuspid: Pacific Ocean, from Unalaska to southern California, 

 ascending the streams, in the Columbia as far as Walla Walla. 



