HISTORY OF THE FISHES OF MASSACHUSETTS. 275 



But it is principally valued as lamp-oil ; for this purpose it is superior to the oil ob- 

 tained from any other fish, and is equal to purified sperm oil. 

 Massachusetts, Storer. 



OEDEE III. CYCLOSTOMI. 



Gills purse-shaped, fixed, opening outwards by several apertures. Jaws represented 

 by an immovable cartilaginous ring, formed by the union of the palatine and mandibular 

 bones. Intestinal canal straight and narrow. 



FAMILY XXX. PETROMYZONIDtE. 



Body elongated, cylindrical, eel-shaped. No pectorals nor ventrals. Fins without 

 rays. 



GENUS I. PETEOMYZON. Lin. 



Seven branchial apertures on each side of the neck. Maxillary ring armed with 

 strong teeth. Mouth beneath. 



Petromyzon americanus. Lesueur. 



The Great Lamprey. 



(Plate XXXVIII. Fig. 4.) 



Peiromyzon marinus, Great Lamprey, Mitch., Trans. Lit. and Phil. Soc. N. Y. i. p. 461. 

 Petromyzon americanus, Lesueur, Trans. Amer. Phil. Soc, new series, i. p. 382. 



" " American lamprey, Storer, Report, p. 195. 



" " American sea lamprey, Dekay, Report, p. 379, pi. 66, fig. 216. 



" " Storer, Synopsis, p. 265. 



Color. Above, olive-brown, mottled with dark brown, almost black, confluent patches ; 

 beneath, of a uniform dull brown. Pupils black, irides golden. 



Description. The anterior portion of the body is cylindrical; the posterior com- 

 pressed. A slight carina is observed upon the back. Head rounded, somewhat flattened 

 on the upper portion in front of the eyes. Snout obtuse. Eyes of moderate size. The 

 distance of the eyes from the snout is less than one twelfth the length of the entire fish. 

 A tubular orifice, a fine in its longest diameter, is seen in front of, between the eyes. 

 Posterior to each eye, are seven large branchial apertures, separated about a quarter of 



