Occasional Papers of the Museum of Zoologv 7 



hi. Dorsal fins well separated by an interspace, except in 

 breeding specimens; oral fimbriae relatively slender, 

 with few marginal incisions ; all teeth sharp and strong 

 (becoming blunt by wear in breeding individuals) ; 

 intestine of adults well developed and functional; 

 larvae at transformation much smaller than the larger 

 adults; not breeding at a size of less than 30 cm. 

 Coasts and streams from Bering Sea zvest to the 

 Jl'hitc Sea and south to the Sea of Japan, 



Entosphcnus jafonicus. 



h-. Dorsal fins separated only by a notch to base; oral 

 fimbriae palmate; all teeth blunt and weak; intestine 

 of adults degenerate and non-functional ; larvae at 

 transformation attaining the adult size (21 cm. or 

 less). Streams of North America and eastern Asia. 



Entosphenus appendix. 



No teeth other tiian the marginals on the posterior field of the 

 disc; three enlarged laterals. 



Genus Lampetra 



ii. Cusps of supraoral always simple, stronger, well separated 

 by a broad bridge; infraoral lamina with 6 to 9 distinct 

 cusps; a series of teeth extending across the entire ante- 

 rior part of the buccal disc within the marginal series; 

 cusps of lateral teeth with a common well-marked base; 

 myotomes between the last gill opening and the vent 58 

 to 70. 



Subgenus Lampetra 



ji. Dorsal fins usually well separated by an interspace; 

 myotomes between the last gill opening and the vent 

 63 to 70; all teeth sharp and strong; intestine of adults 

 well developed and functional; larvae at transforma- 

 tion much smaller than the larger adults. Coasts and 

 streams of northern Eurasia and zvestern North 

 America. Lampetra fimnatilis. 



]-. Dorsal fins separated only by a notch to base; myo- 

 tomes between the last gill opening and vent 57 to 66; 

 all teeth weak and blunt; intestine of adults degen- 

 erate and non-functional; larvae at transformation 

 attaining the adult size. Streams of Eurasia and west- 

 ern North America. Lampetra planeri. 



