CYCLOSTOMES. 



357 



branchial openings placed on each side of the neck, and 

 by their circular mouth, armed with several ranges of 

 strong teeth ; the tongue is also furnished with teeth, and 

 is carried forward and backward like |i piston, thus 

 enabling the animal to use its mouth, not only to suck in 

 the materials upon which it feeds, but to attach itself to 

 solid bodies. The skin of these fishes above and below 

 the tail is raised into a vertical crest, which takes the 

 place of fins. 



The Sea Lamprey (Petromyzon-marinus) is two or three feet 

 long, and marbled with brown on a yellowish ground, it inhabits the 

 coasts both of Europe and America, and in the spring ascends rivers 



FlG. 291. LAMPREY. 



to deposit its eggs. It ordinarily preys upon marine mollusca, or 

 fragments of dead animals ; but it also attaches itself to large fishes, 

 and succeeds in piercing their skin and destroying them. Its flesh 

 is much esteemed. 



The Fresh-water or River Lamprey (Petromyzon fluviatilis) is a 

 smaller species, seldom exceeding eighteen inches in length; it 



FlG. 292. RIVER LAMPREY. 



passes the greater part of the year in fresh-water lakes, which it 

 abandons in the spring to enter rivers. Its colour is dark olive, 

 yellowish, and silvery beneath. 



A third species is. 



The Lampern, or Small River Lamprey, about eight or ten inches 

 in length ; it also inhabits fresh waters, and is distinguished from the 



