INTRODUCTION. 3 
Mammatta (vertebrates suckling their young). 
Prototheria: Oviparous mammals. Ornithorhynchus. 
or duck-bill and Echidna or spiny 
ant-eater. 
Eutheria: 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 cow). 
Ungulata (the hoofed mammals). 
Carnivora (dogs, cats, wolves, and 
foxes). 
Primates (monkeys and man). 
A glance at the above outline shows that the class Mam- 
malia 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 fami- 
lies, of which Canidee (the dogs), Felidee (the cats), and 
Ursidz (the bears) are the most frequently seen in America. 
The family Felidze is represented by only two living genera, 
Cynelurus 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 several varieties, such as 
Maltese, Angora, and Manx cats. 
Linneus, born in Sweden, 1702, invented the system of 
binonual nomenclature in accordance with which the scien- 
tific name of every plant and animal is composed of two 
parts, the generic and specific. Thus the house cat is 
designated Felis domestica; the lion, Felis leo; the dog, 
