INTRODUCTION. 1 9 



Vertebrata : Forms with i\ skeletal axis and dorsal nerve-cord whose 



anterior end is dilated into a brain. 

 PISCES (fish). 



AMPHIBIA (frogs, toads, and salamanders). 

 REPTILIA (snakes and lizards). 

 AYES (birds). 

 MAMMALIA (vertebrates suckling their young). 



I'rutothcria: Oviparous mammals. Ornithorhynchus. 

 Euthcria: Viviparous mammals with anus and 



urogenital opening distinct. 

 Marsupialia (opossums and kangaroos). 

 Insectivora (moles, shrews, and hedge- 

 hogs). 



Edentata (sloths and ant-eaters). 

 Chiroptera (bats and flying foxes). 

 Rodentia (rabbits, squirrels, mice, and 



rats). 



Cetacea (whales, porpoises, and dol- 

 phins). 



Sirenia (sea co\\ ). 

 Ungulata (the hoofed mammals). 

 Carnivora (dogs, cats, wolves, and 



foxes). 

 Primates (monkeys and man). 



A glance at the above outline shows that the class 

 Mammalia is divided into two subclasses, the latter of 

 which includes ten orders. Each of these orders consists 

 of several families which in turn are composed of genera 

 made up of species. The order Carnivora includes eleven 

 families, of which Canidae (the dogs), Felidae (the cats), 

 and Ursidae (the bears) are the most frequently seen in 

 America. The family Felidae is represented by only two 

 living genera, Cynaelurus and Felis. The genus Felis 

 includes several species, of which Felis leo (the lion), 

 Felis tigris (the tiger), and Felis domestica (the cat) 

 are the most familiar. Of the last species, there are sev- 

 eral varieties, such as Maltese, Angora, and Manx cats. 



Linnaeus, born in Sweden, 1702, invented the system 



