Occasional Papers of the Museum of Zoology 5 



gill opening and the vent about 70 in number. North 

 Atlantic Ocean and coastwise streams. 



Petromyzon {Petromyzon) marinus. 



d-. Anterior lingual lamina little bent inward medially^ its 

 edge crenulate, without a differentiated median cusp ; 

 supraoral lamina narrow, with one (usually) or two lobe- 

 like cusps; infraoral lamina with five blunt cusps or 

 crenulations ; all teeth very blunt and greatly reduced in 

 size, particularly on the posterior field ;3 lateral disc teeth 

 about as in Petromyzon marinus, but much weaker; the 

 innermost (enlarged) teeth grading outward into minute 

 teeth aligned in rows deflected backward much more 

 sharply than in Petromyzon marinus ; buccal funnel reduced 

 in size; oral fimbriae smaller than in Petromyzon marinus 

 and less divided ; marginal oral membrane scarcely devel- 

 oped. Caspian Sea and tributaries. 



Petromyzon (Caspiomyzon) wagneri.*^ 



d". Anterior lingual lamina little bent inward medially, usu- 

 ally with an enlarged median cusp ; supraoral lamina broad 

 and bicuspid; infraoral lamina with 9 to 11 cusps; inner- 

 most lateral disc teeth of each side enlarged, the first 

 and third unicuspid or bicuspid, the middle one bicuspid 

 or tricuspid. Transylvania [from Regan]. 



Petromyzon (Eudontomyzon) danfordi.^ 

 Teeth of the buccal funnel not in distinct radiating series, but in 

 several groups : several enlarged lateral teeth, usually multicuspid, 

 at the edge of the oral opening; a marginal series around edge of 

 disc; few to many teeth on the anterior part of the disc; supra- 

 oral broad, the main cusps being separated by a bridge; fins about 

 as in Petromyzon. 



e^. A posterior series of small teeth developed, parallel to the 

 marginal series and connecting the last pair of enlarged laterals. 

 Genus Entosphenus 



3 The posterior disc teeth in Petromyzon wagneri are least obsolete 

 in a single series corresponding to that diagnostically retained in Entos- 

 phenus. 



* Petromyzon wagneri Kessler, "Trud. St. Petersb. Obshch. Estestv., 

 I, 1870, pp. 207, 302, pi. 3, figs. 4, 5"; Caspiomyzon wagneri, Regan, 

 Ann. Mag. Nat. Hist., (8), 7, 191 1, P- 200. The diagnosis here given 

 by us is based upon a series of specimens from Astrachan, Russia 

 (No. 37293, United States National Museum). 



^Eudontomyzon danfordi Regan, Ann. Mag. Nat. Hist., (8), 7, 

 191 1, p. 200. 



