14 University of Michigan 



II. Lampetra lamo\ttenii Le Sueur (Plate I) 

 The name lamottenii Le Sueur*^ is revived for this aberrant 

 brook lamprey, as the obsolescent dentition, partial union of 

 the dorsal fins, and the coloration as shown in the type figure 

 indicate that Le Sueur had the present species. It is the only 

 representative of the genus Lampetra, as now restricted, which 

 occurs in eastern North America. Ammocoetes aepyptera 

 Abbott*^ is its only synonym. It is the most degenerate of all 

 the known lampreys. 



We base on this species a new subgenus, Okkelbergia, named 

 in honor of Dr. Peter Okkelberg, of the University of Mich- 

 igan, in recognition of his careful studies on the history of 

 the germ cells in lampreys. The subgeneric and specific char- 

 acters are both indicated in the diagnostic key (see p. 8). 



*i In DeKay, New York Fauna, Fishes, 1842, p. 382, pi. 79, fig. 249. 

 ■*- Proc. Acad. Nat. Sci. Phila., i860 (1861), p. 2>V, type redescribed 

 by Fowler, ibid., 1901, p. 328; and ibid., 1907, p. 466. 



