UNUTILIZED FISHES. 11 



specimens are taken that measure as much as 5 feet. The distinctive 

 characters of the species are shown in figure 1, plate i. 



The smooth dogfish is of wide distribution. It occurs in great 

 numbers along our Atlantic coast from Cape Cod to Florida, and is 

 found in the Pacific, along the coast of California. It abounds also 

 on the Atlantic coast of southern Europe and in the Mediterranean. 



BREEDING HABITS. 



The mode of reproduction in this species is very difi^erent from that 

 of most other fishes, fertilization being internal. The eggs develop 

 inside of the egg tubes, and the young when born are similar to adults 

 excei:)t in size. They are vigorous and swim about actively. A 

 female smooth dogfish, which was opened in the summer of 1904 by 

 Dr. Linton at the Fisheries' laboratory at Woods Hole, contained 

 8 young, which measured about 12^ inches each. They were about 

 ready to be born. I have never found more than 12 embryos nor less 

 than 4 in a pregnant female. How long a time intervenes between 

 fertilization and birth of the young has not been determined. 



FOOD. 



Several writers in past years have incidentally devoted a paragraph 

 to the food of the smooth dogfish. Xone of them, however, has made 

 a thorough study of the subject. Verrill and Smith (1873) state: 



Several specimens caught at Woods Hole contained lobsters {Homarus aiucri- 

 canus), spider crabs (Libinia canaliculata) , rock crabs (Cancer irroratus) . 



Goode (1884) gives merely the general statement that "it feeds 

 upon crabs, lobsters, and other bottom-loving invertebrates." 

 Linton (1901) says: 



The alimentary canals usually contain crabs {Panopeus, Platyonichus, Cancer, 

 Libinia, etc.) ; squid, annelids, and fish have also been noted. 



In the Standard Natural History, vol. iii, appears the statement: 



It is harmless and feeds on the. crabs and shells which abound on the bottom 

 in favored localities. 



EXAIVIINATION OF DIGESTIVE TRACTS. 



The accompanying table is in general agreement with all that the 

 foregoing writers have said concerning the food of the dogfish, 

 except that the species is not harmless. A careful study of the table, 

 which gives the results of examinations of 388 specimens, will show 

 not only that the smooth dogfish is destructive to crustaceans in gen- 

 eral, but that it is especially the enemy of the valuable American 

 lobster. About IG per cent of the 388 fishes contained lobster in 

 varying (Quantities, from a leg or chela up to two Avhole lobsters 

 measuring as much as 7 inches in length. 



