PLAGIOSTOMI I SQUALIDyE. 



Fig. 238. 



357 



Fig 239. 



Head of Mackerel Shark. 



Mackerel Shark, L. punctata, Storer. 



backed Shark, L. punctata, Storer, is 

 from four to eight feet long, tail with a 

 keel on its side, and the lobes not greatly 

 unequal. 



The Genus Mustelus has the teeth 

 blunt, forming a closely compacted pave- 

 ment in each jaw. The Dog Shark, M. 

 canis, Dekay, is from two to four feet 

 long. 



The Genus Selachus\&& small, smooth 

 teeth, the branchial apertures all before the pectorals, 

 long, and nearly surrounding the neck. The Basking 

 Shark, 5. maximus, Yarrell, exceeds thirty feet in length 

 Although so large, it lacks the ferocity of other species. 



The Genus Somniosus contains the Sleeper, or Nurse 

 Shark, 5. brempinna, LeS., of the eastern coast of North 

 America. It is so sluggish, that it often allows itself to 

 be captured on a cod line. 



The Genus Acanthias has a sharp, stout spine in front of 

 each of the two 

 dorsals. The 

 Dog-Fish, A. 

 americanus , 

 Storer, is from 

 one to three 



Dog-Fish, A. americanus, Storer. 



feet long. It 



is caught in great numbers for the sake of its oil. 



Fig. 240. 



