FISHES OF NEW YORK 33 



ranterior to or slightly over the pectoral base; no nictitating 

 membrane; spiracles minute, just behind the eye, or absent, first 

 dorsal high, triangular, midway between pectorals and ventrals; 

 second dorsal and anal very small; pectorals long and wide, 

 deeply concave behind; ventrals wider than high, below the 

 interspace between the dorsals; caudal without keel, exceed- 

 ingly long and narrow, its lower lobe moderate, its upper lobe 

 with a deep pit at its root and a notch near its tip; size large; 

 a single species inhabiting most warm seas, and easily known by 



its long tail. 



15 Alopias vulpes (Gmelin) 



Thresher Shark; Swingle-twil Shark 



^qualus vulpes Gmelin, L.Syst. Nat. 1, 149G, 1788 (fide Gunther); Mitchill, 



Trans. Lit and Phil. Soc. N. Y. I, 482, 1815. 

 ■Carcliarias vulpes De Kay, N. Y. Fauna, Fishes, 348, pi. LXI, fig. 199, 1842: 



Stoker, Hist. Fish. Mass. 245, pi. XXXVI, fig. 3, 1867. 

 Alopecias vulpes Gunther, Cat. Fish. Brit. Mus. VIII, 393, 1870. 

 Alopias vulpes Jordan & Gilbert, Bull. 16, U. S. Nat. Mus. 27, 1883; 



Jordan & Evermann, Bull. 47, U. S. Nat. Mus. 45, pi. VI, fig. 20, 



1896; Smith, Bull. U. S. F. C. XVII, 89, 1898. 



Body fusiform, moderately elongate, its greatest hight one 

 fourth of the length to the pit at the root of the caudal; head 

 two sevenths of the same length; eye one ninth as long as head; 

 no nictitating membrane; snout short, twice as long as the eye, 

 Flat, triangular teeth of moderate size, with entire edges, in 

 both jaws, the third tooth of the upper jaw on each side much 

 smaller than the others; spiracles just behind the eyes, minute 

 or wanting; gill openings moderate, the last one over the base 

 of the pectoral; first dorsal large, midway between pectorals 

 and ventrals; second dorsal and anal very small; caudal elon- 

 gate, slender, forming about one half of the total length; a pit 

 at its base, upper lobe notched near the tip, lower lobe 

 moderate; no caudal keel; ventrals one half as long as the pec- 

 torals; pectorals falcate, reaching to below the middle of the 

 first dorsal. 



The thresher shark is abundant in the Mediterranean and 

 warm parts of the Atlantic and Pacific, occasionally seen off 

 the south shore of Long Island in summer and frequently taken 

 in Vineyard sound. It reaches a length of 20 feet. 



