246 HISTORY OF THE FISHES OF MASSACHUSETTS. 



The pectorals are large, stout, falciform ; their posterior bases are free. 



The ventrals are shaped like the first dorsal, and are of the same length. 



The anal fin is of the same size and form as the second dorsal, and is situated just pos- 

 terior to it. 



The caudal fin is very strong and powerful ; its inferior base is triangular ; back of 

 this portion it gradually diminishes in thickness and terminates obtusely ; just anterior 

 to the extremity of the tail, upon its inferior edge, is a small triangular portion. A fleshy 

 membrane margins the entire inferior edge of this fin. 



Length, twelve to fifteen feet. 



Remarks. This species, which sometimes weighs from one hundred and fifty to two 

 hundred pounds, is known by our fishermen as the Tliresher or Swingle-tail, from the mo- 

 tions of its tail, which is often used with great force. It is met with in our waters in sum- 

 mer, not often however, pursuing mackerel and manhaden, upon which it feeds. Small 

 numbers are yearly captured in the fall of the year in nets set for mackerel, and occasion- 

 ally a specimen is taken with the hook while fishing for dog-fish. When thus caught, it is 

 secured with much difficulty on account of the constant and powerful thrashing of its tail. 



This fish is considered almost valueless. Its liver, however, contains a small quantity 

 of oil, and when an individual is accidentally taken, this is preserved and sold with the 

 oil from the livers of other species. 



Massachusetts, Storer. New York, Mitchill, Dekay. 



Carcharias Atwoodi, Storer. 



The Man-eater Shark. 

 (Plate XXXVI. Fig. 4.) 

 Carcharias Atwoodi, Stoker, Proceed. Bost. Soc. Nat. Hist., in. p. 7i. 



Color. A leaden gray upon back and sides, and white beneath. The lower portion of 

 the tips and edges of the pectorals are black. 



Description. Depth across from the origin of the dorsals, twenty-three inches ; across 

 from the origin of the pectorals, twenty-six inches ; across from the first branchial orifice, 

 twenty-five inches ; across from the extremities of the ventrals, fourteen inches ; from 

 the tip of the snout to the first branchial orifice the distance is equal to the greatest 

 depth of the fish. The cheeks are very prominent. The eyes are perpendicularly ob- 

 long, their greatest diameter being two inches, their shorter diameter an inch and a half; 



