188 BACKBONED ANIMALS. 
cold waters from ten to fifteen miles off shore. The had- 
dock belongs to this family, and closely resembles the cod 
in habits and appearance. The tom-cod, ling, cusk, and 
pollock, are all allied forms. 
Note.—The Chiasmodus (Fig. 216) is a deep-sea ally ; the top 
of the head, the under jaws, and the fins, all gleam with vivid phos- 
phorescence ; but, more remarkable yet, their jaws work independently 
and alternately as in the snakes, and the stomach is capable of such 
distention that they can swallow fishes twice their own size. 
Fic. 230.—Fierasfer and young, a fish that lives in holothurians and star- 
fishes. A, adult; 2, young. 
The Fierasfer (Fig. 230, 4) is a silvery, eel-like form, 
rarely found out of the digestive canal of holothurians 
(see page 39). One species inhabits a star-fish (Cuda). 
The young (Fig. 230, 8) pass through several changes be- 
fore assuming the adult form. 
Fic, 231.—Young flounder (P. Amerdcanus), showing different positions of 
the eye as it moves over. (After Agassiz.) 
Flounders (Pleuronectide).—When young, the floun- 
der is somewhat cylindrical ; has an eye upon each side, 
and swims vertically like other fishes, Later it sinks to 
