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Sciurus (100–120 sp., including the sub-genera Spermosciurus, Xerus, Macroxus, Rheithrosciurus, and Rhinosciurus), comprises the true squirrels, and occupies the area of the whole family wherever woods and forests occur. The approximate number of species in each region is as follows: Nearctic 18, Palaearctic 6, Ethiopian 18, Oriental 50, Australian (Celebes) 5, Neotropical 30. Sciuropterus (16–19 sp.), comprises the flat-tailed flying squirrels, which range from Lapland and Finland to North China and Japan, and southward through India and Ceylon, to Malacca and Java, with a species in Formosa; while in North America they occur from Labrador to British Columbia, and south to Minnesota and Southern California. Pteromys (12 sp.), comprising the roundtailed flying squirrels, is a more southern form, being confined to the wooded regions of India from the Western Himalayas to Java and Borneo, with species in Formosa and Japan. Tamias (5 sp.), the ground squirrels, are chiefly North American, ranging from Mexico to Puget's Sound on the west coast, and from Virginia to Montreal on the Atlantic coast; while one species is found over all northern Asia. Spermophilus (26 sp.), the pouched marmots, are confined to the Nearctic and Palaearctic regions; in the former extending from the Arctic Ocean to Mexico and the west coast, but not passing east of Lake Michigan and the lower Mississippi; in the latter from Silesia through South Russia to the Amoor and Kamschatka, most abundant in the desert plains of Tartary and Mongolia. Arctomys (8 sp.), the marmots, are found in the northern parts of North America as far down as Virginia and Nebraska to the Rocky Mountains and British Columbia, but not in California; and from the Swiss Alps eastward to Lake Baikal and Kamschatka, and south as 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 Sciuridae, and, according to some naturalists, a distinct family. They inhabit West Africa and the island of Fernando Po.

Extinct Sciuridae.—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 Palaearctic, 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.

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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.

FAMILY 63.—CHINCHILLIDÆ. (3 Genera, 6 Species.)

GENERAL DISTRIBUTION.

NEOTROPICAL NEARCTIC
SUB-REGIONS. | SUB-RECIONS.

PALEARCTIC ETHIOPIAN
SUB-REGIONS. I SUB-REGIONS.

ORIENTAL I AUSTRALIAN SUB-REGIONS. SUB-REGIONS.

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The Chinchillidæ, including the chinchillas and viscachas, are confined to the alpine zones of the Andes, from the boundary of Ecuador and Peru to the southern parts of Chili; and over the Pampas, to the Rio Negro on the south, and the River Uruguay on the east. Chinchilla (2 sp.), the true chinchillas, are found in the Andes of Chili and Peru, south of 9° S. lat., and from 8,000 to 12,000 feet elevation (Plate XVI. vol. ii. p. 40); Lagidium (3 sp.), the alpine viscachas, inhabit the loftiest plateaus and mountains from 11,000 to 16,000 feet, and extend furthest north of any of the family; while Lagostomus (1 sp.), the viscacha of the Pampas, has the range above indicated. The family is thus confined within the limits of a single sub-region.

Extinct Chinchillido.Lagostomus has been found fossil in the caves of Brazil, and in the Pliocene deposits of La Plata. The only known extinct forms of this family are Amblyrhiza and Loxomylus, found in cavern-deposits in the island of Anguilla, of Post-Pliocene age. These are very interesting, as showing the greater range of this family so recently; though its absence from North America and Europe indicates that it is a peculiar development of the Neotropical region.

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FAMILY 64.–OCTODONTIDÆ. (8 Genera, 19 Species.)

GENERAL DISTRIBUTION.

NEOTROPICAL NEARCTIC I PALÆAROTIC ETHIOPIAN I ORIENTAL I AUSTRALIAN SUB-REGIONS. SUB-REGIONS. SUB-REGIONS. BUB-REGIONS. SUB-REGIONS. SUB-REGIONS.

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The Octodontidae include a number of curious and obscure rat-like animals, mostly confined to the mountains and open plains of South America, but having a few stragglers in other parts of the world, as will be seen by our notes on the genera. The most remarkable point in their distribution is, that two genera are peculiar to the West Indian islands, while no species of the family inhabits the northern half of South America. The distribution of the genera is as follows:—Habrocomus (2 sp.), Chili; Capromys (3 sp.), two of which inhabit Cuba, the third Jamaica (Plate XVII. vol. ii. p. 67); Plagiodontia (1 sp.), only known from Hayti; Spalacopus, including Schizodon (2 sp.), Chili, and east side of Southern Andes; Octodon (3 sp.), Peru, Bolivia, and Chili; Ctenomys (6 sp.), the tuco-tuco of the Pampas, the Campos of Brazil to Bolivia and Tierra del Fuego; Ctenodactylus (1 sp.), Tripoli, North Africa; Pectinator (1 sp.), East Africa, Abyssinia, 4,000 to 5,000 feet.

Capromys and Plagiodontia, the two West Indian genera, were classed among the Echimyidae by Mr. Waterhouse, but Professor Lilljeborg removes them to this family.

Extinct Octodontidae.—Species of Ctenomys have been found in the Pliocene of La Plata, and an extinct genus Megamys, said to be allied to Capromys, in the Eocene of the same country. In Europe, Palaeomys and Archaeomys from the lower Miocene of Germany and France, are also said to be allied to Capromys.

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The Echimyidae, or spiny rats, are a family, chiefly South American, of which the Coypu, a large beaver-like water-rat from Peru and Chili is the best known. Two of the genera are found in South Africa, but all the rest inhabit the continent of South America, East of the Andes, none being yet known north of Panama The genera are as follows :-Dactylomys (2 sp.), Guiana and Brazil ; Cercomys (1 sp.), Central Brazil ; Lasiuromys (1 sp.), San Paulo, Brazil; Petromys (1 sp.), South Africa; Myopotamus (1 sp.), the coypu, on the East side of the Andes from Peru to 42° S. lat., on the West side from 33° to 48° S. lat.; Carterodon (1 sp.), Minaes Geraes, Brazil; Aulacodes (1. sp.), West and South Africa ; Mesomys (1 sp.), Borba on the Amazon; Echimys (11 sp.), from Guiana and the Ecuadorian Andes to Paraguay; Loncheres (10 sp.), New Granada to Brazil.

Fossil and Extinct Echimyido.—The genus Carterodon was established on bones found in the Brazilian caves, and it was several years afterwards that specimens were obtained showing the animal to be a living species. Extinct species of Myopotamus and Loncheres have also been found in these caves, with the extinct genera Lonchophorus and Phyllomys.

No remains of this family have been discovered in North America ; but in the Miocene and Upper Eocene deposits of France there are many species of an extinct genus Theridomys, which is said to be allied to this group or to the next (Cercolabidæ). Aulacodon, from the Upper Miocene of Germany, is allied to the West African Aulacodes; and some other remains from the lower Miocene of Auvergne, are supposed to belong to Echimys.

FAMILY 66.–CERCOLABIDÆ. (3 Genera, 13-15 Species.)

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The Cercolabidæ, or arboreal porcupines, are a group of rodents entirely confined to America, where they range from the northern limit of trees on the Mackenzie River, to the southern limit of forests in Paraguay. There is however an intervening district, the Southern United States, from which they are absent. Erethizon (3 sp.), the Canadian porcupine, is found throughout

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