22 COLLEGE ZOOLOGY 



class into ORDERS, each order into FAMILIES, each family into 

 GENERA, and each genus into SPECIES. 



The gray wolf, for example, belongs to the species occidentalis 

 of the genus Canis. This genus, along with others, such as the 

 genus Vulpes, which contains the red fox, constitute the family 

 CANID.E. The CANID.E are included with the bears (family 

 URSHXE), the seals (family PHOCID^E), and a number of other 

 groups of flesh-eating animals in the order CARNIVORA. Fifteen 

 related orders, of which the CARNIVORA forms one, are placed in 

 the class MAMMALIA. Mammals possess hair and mammary 

 giands; these characteristics distinguish them from the five 

 other classes that make up the SUBPHYLUM VERTEBRATA, or ani- 

 mals possessing vertebral columns. The SUBPHYLUM VERTE- 

 BRATA, together with three other SUBPHYLA, usually called 

 primitive vertebrates, are grouped under the PHYLUM CHORDATA, 

 which contains animals possessing at some time in their existence 

 an internal rod-like support known as the notochord. 



The scientific name of any animal consists of the terms used 

 to designate the genus and species; this is commonly followed 

 by the name of the zoologist who wrote the first authori- 

 tative description of that particular species. The scientific 

 name of the gray wolf is therefore written Canis occidentalis 

 Richardson. 



The complete classification of the gray wolf may be shown in 

 outline in the following manner: 



Phylum CHORDATA 



Subphylum VERTEBRATA 

 Class MAMMALIA 

 Order CARNIVORA 

 Family CANID^E 

 Genus CANIS 

 Species OCCIDENTALIS Richardson. 



Zoologists do not agree as to the exact meaning of the term 

 species. One authority gives the following definition: "A 



