38 NEiW YORK STATE MUSEUM 



torais large; ventrals moderate; tail slender; a pit at tlie root 

 of the caudal; the caudal peduncle strongly keeled on each side; 

 caudal fin lunate, its two lobes nearly equal. Size large. 



17 Isurus dekayi (Gill) 



, Mackerel Shark 



Lamna punctata De Kay, N. Y. Fauna, Fishes, 352, pi. 63, figs. 206, 

 20'7, 1842 (not Squahis punctatns Mitchill); Stoeee, Hist. Fisli. Mass. 

 249, pi. XXXyil, fig. 1, 1867. (This is probably Lamna corniihica). 



Isuropsis dekayi Gill, Ann. N. Y. Lye. Nat. Hist. 153, 1861. 



Isurus dekayi Joedan & Gilbeet, Bull. 16, U. S. Nat. Mus. 874, 18S3; 

 JoEDAN & EvEEMANN, BuH. 47, U. S. Nat. Mus. 48, pi. YI, fig. 21, 1898. 



Body fusiform, cylindric, its greatest depth equaling one fifth 

 of the total length, and slightly exceeding the length of the 

 head. The caudal lobes are nearly equal in length, the upper 

 about equal to depth of body. Gill openings wide, the last 

 over the anterior edge of the pectoral base; middle teeth very 

 long, much longer and narrower than the crowdec^, triangular 

 lateral teeth; first dorsal inserted behind pectorals at a distance 

 equal to one fourth of length of head; falcate, its base equal to 

 one third of its distance from tip of snout, its hight nearly one 

 eighth of the total length; pectoral falcate, more than one fifth 

 of total length, and longer than upper caudal lobe; anal and 

 .second dorsal small; caudal keel nearly one fifth of total length; 

 deep pits at the root of the caudal above and below. 



Color dark slate, lighter beneath. De Kay was informed that 

 it is of a deep bottle green in life and the tongue is mottled with 

 black. Storer states that all the upper part of the body is 

 greenish, which becomes of a slate color after death; pupils 

 black; iris dusky. 



The mackerel shark reaches the length of 10 feet. It occurs 

 from Cape Cod to the West Indies; but is rarely captured in 

 most localities. 



De Kay described a specimen 10 feet 2 inches long, taken in 

 New York harbor, October 1840. A somewhat smaller example 

 was caught near the light-ship off Sandy Hook by Capt. C. H. 

 Barnard 16 years earlier than the date of De Kay's description. 

 Storer refers to it as the most common species of shark found in 



