HISTOKY OF THE FISHES OF MASSACHUSETTS. 277 



Peteomyzon nigricans. Lesueur. 



The Bluish Lamprey. 

 (Plate XXXIX. Fig. 6. a. Mouth.) 



Petromyzon nigricans, Lesueur, Trans. Amer. Phil. Soc, new series, vol. i. p. 385. 

 " 27<e bluish lamprey, Storer, Report, p. 197. 

 " The bluish sea lamprey, Dekat, Report, p. 381, pi. 79, fig. 247. 

 " " " '* " " Linsley, Cat. of Fishes of Connecticut. 



" " " " Stoker, Synopsis, p. 517, 265. 



Color. The upper part of the body is of a deep bluish green color ; beneath, bluish 

 white. Pupils black ; hides silvery. On the top of the head, between the eyes, a small 

 white spot exists. 



Description. The body is cylindrical anteriorly, compressed posteriorly, very much so 

 at the tail, which terminates hi a point. The head is oval, flattened on the top ; the 

 length of the head, measured from the snout to the posterior angle of the eye, is less than 

 one eighth the entire length of the fish. The branchial orifices, of equal size, are situated 

 obliquely back of the eyes. The eyes are of moderate size. The mouth is circular ; its 

 diameter is equal to two thirds the length of the head and surrounded by a fleshy mar- 

 gin ; it is armed within by numerous incurved teeth or horny spines, projecting from 

 widened bases resembling the spines with which the Kaise are armed ; these are much 

 larger on the anterior portion of the disk, and quite small upon the posterior portion. 



There are three teeth in the throat ; two higher up than the third, which is in front of 

 and between the others. Posterior to these, is a semicircular bony ridge similar to the 

 jaws of the Orthagoriscus. 



The first dorsal fin is situated on the posterior half of the fish ; it is rounded pos- 

 teriori} 7 . The distance between the dorsals is equal to half the length of the first dorsal. 

 The anterior portion of the second dorsal fin is considerably higher than the first dorsal. 

 This fin is as long again as the first dorsal ; it gradually diminishes in height toward the 

 caudal fin, to which it is attached, and forms with it a continuous fin. 



The caudal fin is a simple membrane, triangular at its termination, and uniting with 

 the anal fin which is very small. 



Length, three to seven inches. 



Remarks. This species is found attached to other species of fishes. It is not unfre- 

 quently affixed to mackerel ; less often to cod ; and still less frequently to haddock. 



Massachusetts, Lesueur, Storer. Connecticut, Linsley. 



