400 ANNUAL REPORT SMITHSONIAN INSTITUTION, 192 8 



III 



Study of a mammalian collection requires as a first step classifica- 

 tion of the material by orders, that is, determining whether a given 

 specimen represents, for instance, the great group of hoofed mam- 

 mals (ungulates), or the flesh-eaters (carnivores), or the gnawers 

 (rodents), or the trunk bearers (elephants), or the true flying mam- 

 mals (bats), or the fish-like mammals (whales and porpoises). 

 Next the specimens are sorted out into the successively smaller sub- 

 divisions of each order, that is, into families (as, among the flesh 

 eaters, the bear family, cat family, and dog family) ; into genera 

 (as, in the dog family, the true dogs, the foxes, the fennecs, and the 

 African hunting dogs) ; and into species (as the dog and wolf, two 

 species of the true dogs as distinguished from foxes, fennecs, and 

 African hunting dogs). Finally, each species is separated into its 

 subspecies or the local forms which it assumes in different parts 

 of its range (as the huge wolf of our northern forests, the smaller 

 wolf of the Arctic tundras, the dark-colored Avolf of Florida, and 

 so forth.) 



Subspecies are distinguished from each other chiefly by size, by 

 shades of color, and by slight peculiarities in the proportionate 

 lengths of various parts (feet, ears, tail), usually small differences not 

 involving deep-lying elements of structure and, more important still, 

 not always present in every specimen. Species are determined by 

 constantly present peculiarities of the same general type, possibly 

 greater in degree than those which distinguish subspecies, and by 

 differences in actual color and in color pattern, quality and distribu- 

 tion of the fur, shape and size of the teeth, or of the individual parts 

 of the teeth, shape and size of the individual bones of the skull. 

 Genera are determined by still greater peculiarities in structure, often 

 including differences in the number of teeth, the number of toes, and 

 so forth, the essential feature of a genus being that it includes a 

 group of species either actually or as a reasonable possibility. 

 Families are determined by larger characters of the same kind as 

 those which distinguish genera, and each family is primarily a cata- 

 gory which includes or might include a group of genera. Finally, 

 the orders of mammals are distinguished from each other by various 

 combinations of the largest and most fundamental characters of all — 

 such as (a) the processes of reproduction (whether the young are 

 hatched from eggs laid in nests or whether they are born alive ; and, 

 if born alive, whether they have or have not been first brought to high 

 development by a special nutritive organ) ; (h) the type of the limbs 

 and feet (whether hoofed, clawed, or serving as paddles, or as true 

 wings) ; and {c) the type of the teeth (whether chiefly adapted to 

 grasping, as in dolphins, to cutting, as in cats, to chopping, as in 



