264 PRINCIPLES OF ANIMAL BIOLOGY 



Phylum. Example, Chordala (the chordates) 



Subphylum. Example, Veriebrafa (the vertebrates) 

 Class. Example, Mammalia (the mammals) 



Subclass. Example, Eutheria (the placental mammals) 

 Order. Example, Rodentia (the rodents) 



Suborder. Example, Sciuromorpha (the squirrel-like rodents) 



Family. Example, Sciuridae (the flying-squirrels, marmots, squirrels 

 and chipmunks) 

 Subfamily. Example, Sdurinae (the marmots, squirrels and chip- 

 munks) 

 Genus. Example, Sciurus (the arboreal squirrels) 



Subgenus. Example, Tamiasciurjis (the red squirrels) 



Species. Example, hudsonicus (the Hudsonian red squirrel) 

 Subspecies. Example, loquax (the southern Hudsonian red 

 squirrel) 



In some groups "divisions" or "sections" are recognized by authors, 

 but these categories have no definite place in the system; that is, they 

 may be introduced to mark off a group of genera, an assemblage of 

 orders, etc. 



The Linnsean system designates the species by two Latin or latinized 

 names, the generic name, a noun, and the specific name, usually an adjec- 

 tive. Thus Natrix is the generic name of a group of water snakes, and 

 Matrix rhombifer and Natrix sipedon are two species of water snakes. 

 This is known as the binomial system of nomenclature. When sub- 

 species are recognized three names are used, the generic, the specific 

 and the subspecific, thus, Thamnophis sirtalis parietalis. The term 

 variety is usually considered synonymous with sub-species in taxonomy, 

 but it may be used to indicate divisions smaller than sub-species, and 

 in one group, the ants (family Formicidse), the systematists regularly 

 recognize and designate divisions smaller than subspecies by name, using 

 four names for each variety (for example, Camponotus herculeanus ligni- 

 perdus noveboracensis, the northern carpenter ant). 



Rules of Nomenclature. — The binomial and trinomial systems of no- 

 menclature have been of great convenience to naturalists. Before their 

 adoption common names were in use in the scientific world and led to 

 much confusion, the same animals being known by different names and 

 different animals by the same name. To make certain that each animal 

 shall have but one scientific name and that no two animals shall have the 

 same name, rules of nomenclature have been proposed at different times 

 for the purpose of determining which name shall prevail when several 

 have been or are likely to be inadvertently proposed for the same form. 

 Linnaeus seems to have appreciated the necessity for rules and to have 

 proposed a set. These rules were not sufficient, and several other codes 

 were proposed, the more important of which were the British Association 

 Code, the American Ornithological Union Code, the Code of the German 

 Zoological Society, and the Code of the International Zoological Congress. 



