PRINCIPLES OF CLASSIFICATION 17 



a single genus. Other squirrel-like animals, as the chip- 

 munk, the flying squirrel, the prairie gopher, or the prairie 

 dog, belong to as many different genera. 



In the binomial system, invented by Linnaeus and ap- 

 plied by him to animals in 1758, the scientific name of an 

 animal consists of two words the name of its genus and 

 species taken together. The name of the genus comes 

 first. It is a noun, in Latin form, though usually of Greek 

 derivation thus Sciurus, the squirrel, in Greek meaning 

 shadow-tail. The name of the species is an adjective in 

 meaning, placed after the noun and agreeing with it. 

 Thus Sciurus hudsonicus is the name of the red squirrel, 

 Sciurus carolinensis of the Eastern gray squirrel, and 

 Sciurus ludovicianus of the fox squirrel ; Sciuropterus 

 volans is the flying squirrel, Tamias striatus the Eastern 

 chipmunk, and Spermophilus franklini one of the prairie 

 gophers. The specific name is usually a descriptive, adjec- 

 tive often the name of a locality, sometimes the name of 

 a man. The authority usually written after the name of 

 an animal is that of the one who gave it its specific name 

 thus Sciurus hudsonicus Erxleben, which means that 

 Erxleben first called it liudsonicus. Usually the name of 

 the authority is that of the discoverer of the species. When 

 several names are given to the same animal they are called 

 synonyms. The earliest of these names is the right name. 

 All the rest are wrong. 



18. Families of animals. A group of related genera is 

 called a family. The name of a family is derived from that 

 of its principal genus, with the termination idee. Thus all 

 the squirrel-like animals belong to the family of Sciuridce. 

 All the sorts of mice to the Muridce, from the principal 

 genus, Mus, the mouse. The rabbits are Leporida, from 

 Lepus, the rabbit, and the beavers Castoridce, from Castor, 

 the beaver. 



19. Higher groups of animals. In the higher groups we 

 first trace out the different plans of structure. There is 



