30 BULLETIN OF THE BUREAU OF FISHERIES 



but its lower lobe is relatively shorter than in either tiger or blue shark. The dusky 

 shark is further distinguished from the latter by its blunt rounded nose and broad 

 flat head. The upper teeth are broad, triangular, serrate, and with concave outer 

 edges; the lower teeth are narrower, more pointed, with broad bases, and stand more 

 erect. 



Size. — This shark occasionally reaches a length of 14 feet, but the larger 

 specimens caught in the traps are usually only 6 to 9 feet long. The relation of 

 length to weight may be judged from the fact that one 11 feet 6 inches in length 

 weighed 650 pounds. 



Color. — Gray brown above; whitish below. It is said that this shark is some- 

 times blue above. 



General range. — Middle Atlantic; from North Carolina to Portland, Me., on 

 the coast of North America. 



Occurrence in the Gulf of Maine. — Like several other sharks the shovelnose is 

 sufficiently plentiful all along the shores of southern New England, as far east as 



Fig. 8.— Dusky shark ( Carcharhinus obscurus) 



Cape Cod, throughout summer and early autumn, to be well known to the local 

 fishermen. At Woods Hole, for example, it is very common, but it rarely strays 

 into the colder waters beyond the cape. The localities within the Gulf of Maine 

 where it has been definitely recorded are Crab Ledge off Chatham, Nahant, Massa- 

 chusetts Bay, and Cod Ledge near Cape Elizabeth (the most northerly occurrence 

 yet known), where one was caught in 1S64 by Capt. B. J. Willard. So rare are 

 these stragglers that neither of the writers has ever seen one in the Gulf. In short, 

 it has no place in the fauna of the latter except as a stray. Neither recorded cap- 

 ture nor fishermen's report credits it to Georges or to Browns Bank. 



Food. — The shovelnose is a bottom swimmer, feeding chiefly on fish and 

 squid but also eating the larger Crustacea, dinners, menhaden, scup, skates, 

 and silver hake have been found in specimens caught at Woods Hole. It is 

 harmless to human beings. 



THE HAMMER-HEADED SHARKS. FAMILY CESTRACIONTID^ 



The peculiar shape of the head, described below, sufficiently characterizes the 

 only Gulf of Maine representative of this family, which otherwise resembles the 

 requiem sharks (p. 27). 



