520 PISCES (CARTILAG.) CYCLOSTOMI. [PETROMYZON. 



preserved. In breadth it is about forty-five inches. The specimen being 

 imperfect, and the characters of some of the species ill-defined, Mr. 

 Thompson hesitates applying to it a specific name. He states, however, 

 that it somewhat resembles the C. Giorna figured by Risso. I have 

 accordingly annexed a reference to that author. 



ORDER IX. CYCLOSTOMI. 



GEN. 77. PETROMYZON, Linn. 



209. P. marinus, Linn. (Sea Lamprey.) Greenish 

 or yellowish brown, marbled with dusky: dorsals separate; 

 the posterior one rounded, just reaching to the caudal. 



P. marinus, Linn. Syst. Nat. torn. i. p. 394. Block, Ichth. pi. 77. 

 Don. Brit. Fish. vol. iv. pi. 81. Turt. Brit. Faun. p. 109. Flem. 

 Brit. An. p. 163. Blainv. Faun. Franc, p. 5. pi. 1. f. 1, & 2. 

 Lampetra Rondeletii, Will. Hist. Pise? p. 105. tab. G. 2. f. 2. 

 Sea Lamprey, Penn. Brit. Zool. vol. in. p. 76. pi. 8. no. 27. Id. 

 (Edit. 1812.) vol. in. p. 102. pi. 10. Bowd. Brit. fr. wat. Fish. 

 Draw. no. 26. La Grande Lamproye, Cuv. Reg. An. torn. n. 

 p. 404. 



LENGTH. From two to two and a half feet ; sometimes more. 



DESCRIPT. (Form.) Anguilliform : body thick and cylindric anteriorly, 

 compressed and somewhat tapering beyond the commencement of the 

 dorsal fin : head indistinct, obtuse and obliquely truncated in front, rather 

 depressed above the eyes: mouth very large, circular, bordered by a 

 fleshy lip, studded on the inside with corneous conical tooth-like papillae 

 disposed in concentric rows, and gradually increasing in size as they 

 advance inwards; beyond these one large tooth below, in the middle, 

 with six or eight points, the extreme points being the most developed ; 

 answering to it above a similar tooth, also in the middle, but with only 

 two points ; tongue with two pairs of crenated teeth : eyes large, lateral, 

 a little in advance of the first branchial opening : a single nostril on the 

 top of the head, in the middle, a little in advance of the eyes, moderately 

 large : line of the branchial apertures a little below the level of the eyes, 

 and rather inclining downwards posteriorly : skin every-where smooth 

 and naked: two distinct dorsals: the first commencing beyond the middle 

 of the entire length, short and low, of a somewhat semicircular form : 

 second commencing a little behind the first, more elevated, and attaining 

 its greatest height rather suddenly, afterwards sloping gradually off, and 

 finally terminating immediately before the caudal : vent very much be- 



