28 INTRODUCTION 



Order e. Chirtip'tera (hand- winged) : Forms adapted for flight. 



Bats, flying foxes (Fig. 310). 

 Order f. Roden'tia (gnawing): Mammals having usually two 



elongated chisel-like incisors in each jaw. Rabbits, squirrels, 



mice, rats (Fig. 309). 

 Order g. Ceta'cea (whale): Marine mammals with fishlike 



body and no hind limbs. Whales, porpoises, dolphins. 

 Order h. Siren'ia (siren) : Aquatic forms with no hind limbs. 



Sea cow. 

 Order i. Ungula'ta (bearing hoofs): Mammals which have 



hoofed feet. Horse, cow, pig. 

 Order j. Carnlv'ora (flesh-eating): Mammals living on flesh 



and with strong canine teeth and claws. Dogs, cats, wolves, 



foxes. 

 Order k. Primates (first) : Mammals with thumb opposable to 



the other digits. Lemurs, monkeys, man. 



A glance at the above outline shows that the entire ani- 

 mal kingdom, consisting of a half million species, is divided 

 into thirteen subkingdoms sometimes called phyla or 

 branches. Each of these is composed of several classes, 

 but in most cases the names of the classes are not given. 

 The divisions of the classes are designated orders which 

 in turn are divided into families. A family is composed 

 usually of several genera, and each genus is still further 

 divided into species. 



Linnaeus of Sweden invented the system of binomial 

 nomenclature, in accordance with which the name of every 

 plant or animal is composed of two parts, the generic 

 which is a noun, and the specific, which is an adjective. 

 Thus, the house cat is called Fells domestica; the lion 

 Felis leo ; the dog, Canis familiaris; the wolf, Canis latrans; 

 the red squirrel, Sciurus hudsonicus ; the gray squirrel, 

 Sciurus carolinensis. Animals of the same genus but of 



