Occasional Papers of the Museum of Zoology 3 



Genus Entosphenus Gill. 



Subgenus Tetrapleurodon (new). 



Entosphenus spadiceus Bean (no figure). 



Subgenus Entosphenus Gill. 



Entosphenus tridentatus tridcntatus Gairdner : Lucas, Rept. 

 Fur-Seal Invest., pt. 3, 1896-1897 (1899), pi. 15. 

 Entosphenus tridentatus cUiatus Ayres (no figure, but dentition 

 as in typical tridentatus) . 



Subgenus Lethenteron (new). 



Entosphenus japonicus Martens: Smitt, Hist. Scand. Fishes, 

 pt. 2, 1895, p. 1 191, fig. 353 (as "F. fluviatilis Var."). 

 Entosphenus appendix DeKay: Gage, The Wilder Quarter- 

 Century Book, 1893, pi. 6, fig. 21; Forbes and Richardson, 

 The Fishes of Illinois (Nat. Hist. Surv. 111., Vol. 3, Ed. i, 

 1908, and Ed. 2, 1920, p. 11, fig. 10). 



Genus Lampetra Gray. 



Subgenus Lampetra Gray. 



Lampetra fluviatilis Linnaeus : Giinther, An Introduction to 



the Study of Fishes, 1880, p. 692, fig. 316; Bade, Die mittel- 



europaischen Siisswassernsche, 2, 1902, p. 106, figs. 77, 78. 



Lampetra planeri Bloch : Bade, Die mitteleuropaischen Siiss- 



wasserfische, 2, 1902, p. 109, fig. 82. 

 Subgenus Okkelbergia (new). 



Lampetra lamottenii Le Sueur : Creaser and Hubbs, pi. i 



(present work). 



A Diagnostic Key to the Hoearctic Lampreys 

 In the construction of this key an attempt is made to 

 express the probable relationships of the Holarctic lampreys, 

 and to make the diagnosis of any subdivision sufficiently com- 

 plete to serve as its definition. 



Family Petromyconidae 



a^. Buccal funnel with series of teeth radiating in all directions from 

 the mouth, deflected backward toward the margin of the disc, 

 b^. A single more or less deeply emarginate dorsal fin ; dorsal fin 

 not separated from the caudal by a sharp notch ; caudal a 

 broadly oval lobe ; innermost lateral disc teeth usually uni- 

 cuspid ; base of teeth poorly developed ; myotomes between 

 last gill opening and the vent fewer than 60 (49 to 57). 

 Genus Ichthyomyzoh 



