534 THE OCEAN WORLD. 
rudimentary skull without any trace of true bony appendages. 
There are no jaws, but the inner surface of the mouth is often 
armed with teeth. Their gills, in place of presenting the comb-like 
appearance of other fishes, have something of the form of little sacs. 
The lampreys may be considered as the type of this family. ; 
The Lampreys (Peromyzon) are cylindrical eel-like fish, with 
seven gill-openings on each side of the neck, forming two longitudinal 
lines; mouth round, armed with many teeth. The Sea Lamprey 
Fig. 356,—The Lamprey (Petromyzon marinus). 
P. marinus (Fig. 356), belongs to the Mediterranean ; it is also found 
in the German Ocean, and is not rare along the coasts of great 
Britain and Ireland. In the spring it ascends the rivers, where it is 
sometimes caught in abundance. Full-grown it is about three feet 
long, its colour is a marbled brown upon yellow ; the dorsal fins are 
separated by long intervals; its mouth is circular and surrounded by 
a fleshy lip, furnished with cirri, having a cartilaginous plate for sup- 
port ; it is provided on its internal surface with many circular rows of 
strong teeth, some single, the others double. 
The Lamprey feeds on worms, molluscs, and small fishes ; its 
mouth is a powerful sucker, by the aid of which it attaches itself to 
rocks and stones under water. It is taken by hook and line, but is 
