546 The True Sharks 



haul of the net. They are very destructive to herrings and other 

 food-fishes. Usually the fishermen cut out the liver, throwing 

 the shark overboard to die or to be cast on the beach. In 

 northern Europe and New England Squalus acanthias is abun- 

 dant. Squalus sucklii replaces it in the waters about Puget 

 Sound, and Squalus mitsukurii in Japan and Hawaii. Still 

 others are found in Chile and Australia. The species of Squalus 

 live near shore and have the gray color usual among sharks. 

 Allied forms perhaps hardly different from Squalus are found in 

 the Cretaceous rocks and have been described as Centrophoroides. 

 Other genera related to Squalus live in greater depths, from 100 

 to 600 fathoms, and these are violet-black. Some of the deep- 

 water forms are the smallest of all sharks, scarcely exceeding a 



a 4 



FIG. 339. Etmopterus lucifer Jordan & Snyder. Misaki, Japan. 



foot in length. Etmopterus spinax lives in the Mediterranean, 

 and teeth of a similar species occur in the Italian Pliocene 

 rocks. Etmopterus lucifer* a deep-water species of Japan, has a 

 brilliant luminous glandular area along the sides of the belly. 

 Other small species of deeper waters belong to the genera 

 Centrophorus, Centroscymnus, and Deania. In some of these 

 species the scales are highly specialized, pedunculate, or having 

 the form of serrated leaves. Some species are Arctic, the others 

 are most abundant about Misaki in Japan and the Madeira 

 Islands, two regions especially rich in semibathybial types. 

 Allied to the Squalida is the small family of Oxynotidcs with 

 short bodies and strong dorsal spine. Oxynotus centrina is found 

 in the Mediterranean, and its teeth occur in the Miocene. 



Family Dalatiidae. The Dalatiida, or scymnoid sharks, differ 

 from the Squalida almost solely in the absence of dorsal spines. 

 The smaller species belonging to Dalatias (Scymnorhinus ; or 

 Scymnus), Dalatias licha, etc., are very much like the dog- 



* Dr. Peter Schmidt has made a sketch of this little shark at night from a 

 living example, using its own light. 



