348 NEW-YORK FAUNA. 



ORDER II. PLAGIOSTOMI. 



Gills fixed by their external edges, ivith five small external openings on each side. No 

 opercle. Jaws represented by the palatine and postmandibulary bones, which alone are 

 armed with teeth. Pectorals and ventrals always present; the latter (in the male) fur- 

 nished on their internal margins with long appendages. 



FAMILY SQUALID^. 



Body elongated, cylindrical. Tail thick and muscular. Eyes lateral. Brayichial openings 

 on each side, never underneath. 



Obs. About eighty species have been described, belonging to this family. 



GENUS CARCHARIAS. Cuvier. 



Snout depressed ; the nostrils beneath the middle. Teeth cutting, pointed, and generally 

 denticulated at the sides. First dorsal far in advance of the ventrals ; the second nearly 

 opposite to the anal, which is always present. No temporal orifices ; the last of the bran- 

 chial openings above or slightly in front of the pectorals. 



THE THRESHER SHARK. 



Carcharias tclpes. 



PLATE LXI. FIG. 199. Female. — (AMERICAN MUSEUM.) 



Long-tailed Shark. Pennant, Br. Zoology. 



Thresher. Mitchill, Medical Repository, Vol. 8, p. 77, figure. (Male.) 



Squatus vulpes, Thresher or Long-tailed Shark. Id. Lit. and Phil. Soc. Vol. 1, p. 482. 



Carcharias vulpes. Cuvier, Rdgne Animal, Vol. 2. 



C. id., Fox Shark, Thresher. Stoker, Report on the Fishes of Massachusetts. 



Characteristics. Upper lobe of the tail nearly as long or longer than the body. Length 

 twelve to fifteen feet. 



Description. Body cylindrical, thickest before the dorsal fin, with a ridge on its upper sur- 

 face towards the tail, and a deep cavity at the base of the caudal fin, as if strangulated. 

 Back regularly arched from above the pectorals to the end of the snout, which is blunt. Skin 

 roughened with minute prickles, which are directed backward, and obvious to the touch. 

 Nostrils small and valvular. Mouth in the shape of a horseshoe, with three series of distant, 

 flat, triangular, smooth-edged teeth in each jaw ; the teeth appear to be loosely inserted in the 



