ZOOLOGY 



Having considered the bony fishes in detail, we may take 

 up the other classes of fishes. 



The lamprey eels, or Cyclostomi, are the only parasitic 

 vertebrates. In the adult stage they either live attached to 



Fig. 304. 



■ Petromyzon, the lamprey. One-fourth nat. size. After Goode. 



the outside of other fishes, sucking their blood, or else they 

 may penetrate into the body ca\nty. They do not bite, l^e- 

 cause thej' have no lower jaw, and are known as " round- 

 mouthed " eels.' Lampreys arc found in the seas and in the 

 rivers of tlie temperate zones. They occur on our Eastern 

 coast and ascend rivers ; others live in the lakes of New York, 



Fig. .30.5. — Aripenser, the sturgeon. One-sixteenth nat. size. After 



Goode. 



in the Great Lakes, and in the Mississippi ^'allej-. Lr Europe 

 they arc much esteemed as food. 



The sharks and rays (Selachians) include all inhabitants 

 of the sea. They may be distinguished from the bonj' fishes 

 by the rough skin, Ix-set with spines, and by a .skeleton that 

 is made not of bone, l)ut of cartilage. We have a number 



1 Fig. 304. 



