16 UNUTILIZED FISHES. 



bothered by the dogfishes coming up and seizing it by the legs, but 

 no harm came to the loon from this experience. 



Besides the few sharks, skates, and dinners, there were put into 

 the pool a number of menhaden which had been inoculated with a 

 germ known to cause a disease in this fish. It was noticed that as 

 long as the menhaden remained normally active they were not 

 molested by the dogfish, but as soon as one began to show signs of 

 the disease by turning on its side and sAvimming in circles, it was 

 attacked and eaten by the dogfish. 



It is pretty safe to conclude, therefore, that the smooth dogfish is 

 normally a bottom feeder and does not prey upon active fishes like 

 bonito, menhaden, scup, etc., unless in close quarters with them or 

 unless it encounters them in a weakened, helpless condition. It feeds 

 j)rimarily upon crustaceans, chief among which are the rock crab, 

 spider crab, and the lobster. To diminish by 95 per cent the number 

 of teleost fishes given in the foregoing list as destroyed by every 

 100,000 smooth dogfish would be much more nearly to approximate 

 the actual truth. The number of crustaceans consumed is probably 

 much greater than the estimate. 



THE SAND SHARK. 



GENERAL CHARACTERS. 



The sand shark {Carcharias littoralis) has an elongate body, which, 

 however, is much heavier than that of the smooth dogfish; the head is 

 rather pointed, mouth ventral, and jaAvs set with long, very sharp 

 teeth; skin covered with sharp tubercles, Avhich are larger and far 

 less numerous than those of the smooth dogfish. The sand shark is of 

 a gray color and measures from 4 to 6 feet in length. According to 

 Jordan and Evermann it is " rather common on our Atlantic coast, 

 especially between Cape Cod and Caj^e Hatteras." 



FOOD. 



But two references to the food of the sand shark have been found. 

 Verrill and Smith (1873) say: 



Many specimens taken at Woods Hole in July and August contained lobsters 

 (Homarus americanus) in abundance, Cancer irroratus, and squids (Loligo 

 pealii). 



Linton (1901) reports: 



Fish (menhaden, sea bass, scup, and butterflsh noted) and squid. 



EXAMINATION OF DIGESTIVE TRACTS. 



During July and August, 1904, 66 sand sharks were examined for 

 the jjurpose of determining their food. The results are given in the 

 accompanying table. 



