HISTORY OF THE 



225 



GENUS II. LAMNA, Cuv. 



Muzzle pyramidal, under the base of which are the nostrils. Branchial apertures an 

 in front of the pectorals. 



Lamna punctata, Storer 





The Mackerel Shark. 



(Plate XXXVII. Fig. I.) 



Squalus punctatus, Green-backed Shark, Mitchill, Trans. Lit. and Phil. Soc. of N. Y., i. p. 483 

 [jamna punctata, Mackerel Shark, Storer, Report, 185, pi. 3, fig. 2. 



" " " " " Bost. Journ. Nat. Hist, n. p. 534. 



" Mackerel Porbeagle, Dekay, Report, p. 352, pi. 63, fig. 206, 207. 

 Lamna punctata, Mackerel Shark, Storer, Synopsis, p. 252. 



Color. All the upper part of the body is greenish, which becomes of a slate color 

 after death ; lighter upon the sides ; white beneath. Pupils black, irides dusky. 



Description. Head small, its length is nearly equal to one seventh the length of the 

 entire fish. Eyes nearly circular, very movable in their orbits; distance between the 

 eyes equal to three times their diameters. Nostrils large, in front of eyes and inferior to 

 them ; the posterior opens forward, and is the larger ; a semicircular groove passes for- 

 ward and downward to the inferior which opens posteriorly. On a line above the eyes, 

 are seen a series of mucous pores, resembling black orifices, running toward the snout ; 

 another series between the eyes and the snout. These are also distributed upon the 

 under portion of the snout. Each jaw is furnished with three rows of small, sharp, 

 triangular teeth, smooth at their edges ; the two first rows straight, the back row re- 

 curved ; the three teeth on each side of the middle of the lower jaw, the largest. Tongue 

 large, rough, fleshy. Eive large branchial apertures situated vertically; the distance 

 between the anterior greater than that between the posterior. The depth of the fish, 

 in front of the dorsal fin, is less than one quarter the length of the fish ; the distance 

 from the extremity of the snout to the dorsal fin is less than one third the length of the 

 fish. 



The first dorsal fin is somewhat triangular, with a fleshy horizontal process pointing 

 backward from its base posteriorly, higher than long, emarginated posteriorly, rounded 

 above. 



The second dorsal fin is adipose, rhomboidal ; its height is equal to one fourth the length 



of the first dorsal. 

 vol. ix. 32 



