The True Sharks 203 
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 mitsukurit 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 
aé 
Fig. 145. —Etmopterus lucifer Jordan & Snyder. Misaki, Japan. 
foot in length. Etmopterus spinax lives in the Mediterranean, 
and teeth of a similar species occur in the Itaian 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 Squalide is the small family of Oxynotide with 
short bodies and strong dorsal spine. Oxynotus centrina is found 
in the Mediterranean, and its teeth occur in the Miocene. 
Family Dalatiide.—The Dalatiid@, or scymnoid sharks, differ 
from the Squalide 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 iight. 
