THE SMELT ANU ITS ALLIED 



247 



commonest (Fig. 230). They are all carnivorous animals 

 and powerful swimmers. They feed on the larger Crus- 

 tacea and fish. 



The living Ganoidei are a remnant of a very extensive 

 group which existed in geological times. North America 

 is especially rich in existing representatives of this group, 

 as of several other old groups, such as the turtles, tailed 

 amphibians, and the king-crab. Of the five families of 

 ganoids, four are represented in this country. In the 

 following four paragraphs we shall consider a type of each 

 of the native families. 



The sturgeons have five rows of bony scales on the 

 trunk and four barbels on the head. 1 They occur both 



FIG. 231. Acipenser, the sturgeon. One-sixteenth nat. size. After Goode. 



in the sea and in the Great Lakes and the rivers of the 

 Central States. Although of large size, they feed for the 

 most part on small aquatic animals, such as worms, insect 

 larvse, and small fish. The flesh of some species is much 

 used as food ; the eggs taken from the ovaries (roe) con- 

 stitute a delicacy known as "caviare." 



The spoonbill, which has an elongated, flattened snout 

 and is almost without scales, is a large fish found in 

 the Mississippi River. It is also called u paddle-fish " or 

 " duck-bill catfish." It becomes two metres long and seeks 

 small animals in the mud, which it stirs up with its snout. 



i Fig. 231. 



