

ZOOLOGY, 



NUMBER OF VERTEBRATE, MOLLUSCOUS, ARTICULATED, AND 



RADIATED ANIMALS. 



THE number of vertebrated animals may be estimated at 20,000. 

 About 1,500 species of mammals are pretty precisely known, and the 

 number may probably be carried to about 2.000. 



The number of birds well known is 4,000 or 5,000 species, and the 

 probable number is 6,000. 



The reptiles number about the same as the mammals, 1,500 

 described species, and they will probably reach the number of 

 2,000. 



The fishes are more numerous ; there are from 5,000 to 6,000 spe- 

 cies in the museums of Europe, and the number may probably amount 

 to 8,000 or 10,000. 



The number of mollusks already in collections probably reaches 

 8,000 or 10,000. There are collections of marine shells, bivalve and 

 univalve, which amount to 5,000 or 7,000; and collections of land 

 and fluviatile shells, which count as many as 2,000. The total num- 

 ber of mollusks would, therefore, probably exceed 15,000 species. 



Among the articulated animals it is difficult to estimate the num- 

 ber of species. There are collections of coleopterous insects which 

 number 20,000 to 25,000 species; and it is quite probable, that, by 

 uniting the principal collections of insects, 60,000 or 80,000 species 

 might now be counted ; for the whole department of Articulata, com- 

 prising the Crustacea, the Cirrhipeda, the insects, the red-blooded 

 worms, the intestinal worms, and the Infusoria, as far as they belong 

 to this department, the number would already amount to 100,000; 

 and we might safely compute the probable number of species actually 

 existing at double, that sum. 



Add to these about 10,000 for Radiata, Echini, star-fishes, Medusae, 

 and Polypi, and we have about 250,000 species of living animals ; 

 and supposing the number of fossil species to equal them, we have, 

 at a very moderate computation, half ft million of species. Princi- 

 ples of Zoology, by Agassiz and Gould, Part I. 



