474 COLLEGE ZOOLOGY 



6. FOSSIL FISHES 



A large number of species of fish are known only from their 

 fossil remains. The earliest fish remains consist of spines and 

 scales from the lower Silurian or Ordovician strata of the earth's 

 crust, which were laid down probably twenty-five million years 

 ago (see Table XVII). The slightly younger Devonian age 

 is called the " Age of Fishes " because of the predominance of 

 fishes over the other animals that lived at that time. A con- 

 siderable portion of the TELEOSTOMI are fossils; four of the 

 five families of the CROSSOPTERYGII; five of the seven families 

 of the CHONDROSTEI; six of the eight families of the HOLOSTEI; 

 and about fifteen families of the TELEOSTEI are fossil forms. 

 In the DIPNOI there are two families of fossil and two of living 

 species. The study of fossil fishes is very important because of 

 the light these prehistoric forms shed upon the affinities of 

 modern species. 



7. THE ECONOMIC IMPORTANCE OF FISHES 



Fishes furnish an important article of food for man, and many 

 of them provide a means of recreation because of the difficulty 

 of hooking them and the desperate struggles they make before 

 they can be captured. Most game-fishes are also useful as food, 

 but this is not always the case; for example, the tarpon which 

 occurs on our Atlantic coast is the greatest of game-fishes, but 

 is not ordinarily eaten by man. A few species are injurious be- 

 cause of the number of food-fishes and other valuable animals 

 they destroy. 



The value of the fishing industry may be judged from sta- 

 tistics obtained at Boston and Gloucester, where about seven 

 eighths of all the fish captured offshore along the Atlantic coast 

 are brought by the fishermen. During the calendar year 1908, 

 181,465,000 pounds of fish, worth to the fishermen $4,629,000, 

 were landed at these two cities. The most important species 



