far as the Himalayas, above 8,000 feet elevation. _Cynomys_ (2 sp.), the prairie-dogs, inhabit the plains east of the Rocky Mountains from the Upper Missouri to the Red River and Rio Grande (Plate XIX., vol. ii. p. 129). _Anomalurus_ (5 sp.), consists of animals which resemble flying-squirrels, but differ from all other members of the family in some points of internal structure. They form a very aberrant portion of the Sciuridæ, and, according to some naturalists, a distinct family. They inhabit West Africa and the island of Fernando Po. {236}_Extinct Sciuridæ._--These are tolerably abundant. The genus Sciurus appears to be a remarkably ancient form, extinct species being found in the Miocene, and even in the Upper Eocene formations of Europe. _Spermophilus_ goes back to the Upper Miocene; _Arctomys_ to the Newer Pliocene. Extinct genera are, _Brachymys_, _Lithomys_ and _Plesiarctomys_, from the European Miocene, the latter said to be intermediate between marmots and squirrels. In North America, _Sciurus_, _Tamias_, and _Arctomys_ occur in the Post-pliocene deposits only. The extinct genera are _Ischyromys_, from the Upper Miocene of Nebraska; _Paramys_, allied to the marmots, and _Sciuravus_, near the squirrels, from the Eocene of Wyoming. Here we have unmistakable evidence that the true squirrels (_Sciurus_) are an Old World type, which has only recently entered North America; and this is in accordance with the comparative scarcity of this group in South America, a country so well adapted to them, and their great abundance in the Oriental region, which, with the Palæarctic, was probably the country of their origin and early development. The family, however, has been traced equally far back in Europe and North America, so that we have as yet no means of determining where it originated. FAMILY 62--HAPLOODONTIDÆ.--(1 Genus, 2 Species.) GENERAL DISTRIBUTION. __________________________________/\__________________________________ / \ NEOTROPICAL| NEARCTIC |PALÆARCTIC | ETHIOPIAN | ORIENTAL | AUSTRALIAN SUB-REGIONS|SUB-REGIONS|SUB-REGIONS|SUB-REGIONS|SUB-REGIONS|SUB-REGIONS. -----------+-----------+-----------+-----------+-----------+------------ | | | | | -- -- -- --|1 -- -- -- |-- -- -- --|-- -- -- --|-- -- -- --|-- -- -- -- | | | | | The genus _Haploodon_ or _Aplodontia_, consists of two curious rat-like animals, inhabiting the west coast of America, from the southern part of British Columbia to the mountains of California. They seem to have affinities both with the beavers and marmots, and Professor Lilljeborg constitutes a separate family to receive them. {237}FAMILY 63.--CHINCHILLIDÆ. (3 Genera, 6 Species.)