_Mammalian Families Peculiar to America._--While there are many genera and species of mammals found only on this continent, the number of families that are peculiar to it is small. Among the characteristic families, most of which, however, extend into South America, none are of greater interest in the study of geographical distribution than the opossums, of which there are 3 genera and some 22 species, all of them confined to the New World. Of these, two species are common in North America: one, the Virginia opossum, abundant throughout the eastern portion of the United States to the south of New York, and the other and smaller species, which inhabits Mexico and extends northward into southern California and Texas. Many representatives of this same family occur in Central and South America, some of which are notable on account of their diminutive size. The opossums are of peculiar interest owing to the fact that they are the only representatives of the marsupials now living outside of Australia. Fossil species occur, however, in the Tertiary rock of Europe, so that the American forms cannot be considered as indicating a recent land connection between this continent and Australia. The porcupines are also representative of the New World fauna, although not strictly confined to it, and belong mostly in the northern continent. The Canadian porcupine is found throughout nearly the entire forested portion of the boreal region and extends as far south as the Middle Atlantic States, and an allied species, but of larger size, inhabits a portion of the same region and extends to the Pacific mountains and occurs in Alaska. The racoons are strictly American and inhabit both continents. They are common in the forests of Central America and Mexico, and extend as far north as central Canada. Of the several families of smaller and less well-known mammals peculiar to this continent, mention may be made of the pouched rats of California. All of the animals to which attention has thus far been directed are now living; should one attempt to describe the great number of fossil forms whose bones have been discovered in the rocks, the menagerie would be vastly enlarged, and many exceedingly strange species, genera, families, and even larger divisions of the animal kingdom, added to the extended procession. THE BIRDS When one attempts to write an account of the birds of North America, the heavens seem darkened with such a multitude of varied and beautiful forms and the air filled with such a discordant clamour mingled with the sweetest of music that failure to convey an adequate idea of the countless numbers and diversity of the feathered throng within the compass of a few pages must be recognised from the start. The important place held by the birds of North America in the avifauna of the world, may perhaps be best indicated by noting first of all what orders and families are without representatives among them.