288 North Ameriran Species of Petromyzontidce. 



Having made use of notes and suggestions from Dr. Burt G. 

 Wilder and Prof. Simon H. Gage, I have the following to offer : 



I have examined in all 106 specimens from Caynga Lake. 

 Of these, 64 possess the prominent dorsal ridge, on the remain- 

 ing 42 the ridge is obsolete or less prominently developed. 



The ridge was considered by me as a sexual distinction (pre- 

 sent on males only), until I found gravid females with the ridge 

 quite prominent. 



The papilla at vent also proved to be rather an unsafe guide, 

 and so I resorted to an examination of the ovaries or testes. 

 This was equally unsatisfactory. A few very doubtful cases 

 were referred to Prof. Gage for microscopical examination, which 

 resulted in more doubt than ever. He did not think that he 

 could tell with absolute certainty which were males or which 

 were females, without some previous study of fresh specimens. 

 All that is left is to get these and study them from a sexual 

 standpoint, which thing we intend to do as soon as possible. 



It seems to me that the question has this value in classifica- 

 tion : if we find that the dorsal ridge is peculiar to the lampreys* 

 of Cayuga Lake, that all males possess it, and no males are found 

 without it, it is a character of specific rank. If on the other 

 hand, males are found without the dorsal ridge as well as with 

 it, and the same prove true of females, the character is without 

 value in classification. 



It may be the case that the ridge is to the lampreys as 'iiorns" 

 are to some minnows, but I hardly think so. 



There are no whole specimens from the Atlantic in the Cor- 

 nell University Museum. A few are here in sections, having 

 been used for class study. The dentition of these is the same as 

 that of the Caynga Lake specimens. 



The mandibulary cusps are as follows : 



Sea lampreys (Heads), 2 with 7 cusps. 



8 



* Since the above was written, Mr. Meek has shown that the dorsal ridge 

 is present in many specimens of P. marinus (from Lawrence, Mass.), and 

 that no distinction exists between the latter and the Cayuga Lamprey, except 

 that the latter does not reach the fult size of the former. 



