198 FISHES OF MASSACHUSETTS. 



as 2 to 8. The distance between the dorsals, is equal to half 

 the length of the first dorsal. 



The second Dorsal is considerably higher than the first ; be- 

 fore reaching the caudal fin, to which it is continued, it is 

 depressed. 



The Caudal fin is a simple membrane, triangular at its ter- 

 mination, and uniting with the anal fin, which is very small. 

 Anus small. 



Le Sueur dwells upon the " white dorsal fins ;" his speci- 

 men was six inches long. My three specimens, one, five 

 inches, a second, six inches in length, have both dorsals per- 

 fectly white ; in the specimen just described, seven inches 

 long, the margin of the second dorsal is of the same color as 

 the back of the fish. 



Ammocoetes. Dumer. 



Generic characters. Form of the body, the branchial aper- 

 tures and fins, like those of the Lampreys ; upper lip semicir- 

 cular, with a straight, transverse under lip ; mouth without 

 teeth, but furnished with numerous short membranous cirrhi. 



A. bicolor. The Mud Lamprey. 

 Trans, of Amer. Phil. Soc. new series, vol. i. p. 386. 



I have never been able to procure this species, and therefore 

 extract Le Sueur's description, drawn up from a specimen sent 

 him from Northampton, by Dr. Hunt, which was taken in the 

 Connecticut river : 



" Dorsal fins low, separated ; the second united with the 

 caudal fin, which is rounded ; back and sides, reddish ; abdo- 

 men white ; the color separated by an undulating line. Ante- 

 rior part of the body subcylindric, posterior part compressed, 

 and tapering to the tail ; nape of the neck elevated ; head de- 

 clivous, prolonged into a snout furnished with a lip having 

 two short rounded lobes ; these lobes, when the mouth is 



