18 INTRODUCTION. 



founded upon some of the minor peculiarities of anatomical 

 structure, such as the number, disposition, or proportions 

 of the teeth, claws, fins, &c., and usually includes several 

 kinds. Thus, the lion, tiger, leopard, cat, &c., agree in the 

 structure of their feet, claws, and teeth, and they belong to 

 the genus Felis ; while the dog, fox, jackal, wolf, &c., have 

 another and a different peculiarity of the feet, claws, and 

 teeth, and are arranged in the genus Canis. 



The Species is founded upon less important distinctions, 

 such as color, size, proportions, sculpture, &c. Thus we 

 have different kinds, or species, of duck, different species 

 of squirrel, different species of monkey, &c., varying from 

 each other in some trivial circumstance, while those of each 

 group agree in all their general structure. The specific 

 name is the lowest term to which we descend, if we except 

 certain peculiarities, generally induced by some modification 

 of native habits, such as are seen in domestic animals. 

 These are called varieties, and seldom endure beyond the 

 causes which occasion them. 



Several genera which have certain traits in common are 

 combined to form a family. Thus, the ale wives, herrings, 

 shad, &c., form a family called Clupeidee ; the crows, black- 

 birds, jays, &c., form the family Corvidse. Families are 

 combined to form orders, and orders form classes, and finally, 

 classes are combined to form the four primary divisions, or 

 departments, of the Animal Kingdom. 



For each of these groups, whether larger or smaller, we 

 involuntarily picture in our minds an image, made up of the 

 traits which characterize the group. This ideal image is 

 called a TYPE, a term which there will be frequent occasion 

 to employ in our general remarks on the Animal Kingdom. 

 This image may correspond to some one member of the 

 group ; but it is rare that any one species embodies all our 

 deas of the class, family, or genus to which it belongs. 



