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last Catalogue (1873) he divides the genus into three—Hyraa, Euhyraa, and Dendrohyraa –the latter consisting of two species confined apparently to West and South Africa. No extinct forms of this family have yet been discovered; the Hyracotherium of the London clay (Lower Eocene) which was supposed to resemble Hyrax, is now believed to be an ancestral type of the Suidae or swine. g
The Muridae, comprising the rats and mice with their allies, are almost universally distributed over the globe (even not reckoning the domestic species which have been introduced almost everywhere by man), the exceptions being the three insular groups belonging to the Australian region, from none of which have any species yet been obtained. Before enumerating the genera it will be as well to say a few words on the peculiarities of distribution they present. The true mice, forming the genus Mus, is distributed over the whole of the world except N. and S. America where not a single indigenous species occurs, being replaced by the genus Hesperomys ; five other genera, comprehending all the remaining species found in South America are peculiar to the Neotropical region. Three genera are confined to the Palaearctic region, and three others to the Nearctic. No less than twelve genera are exclusively Ethiopian, while only three are exclusively Oriental and three Australian.
Mus (100-120 sp.) the Eastern Hemisphere, but absent from the Pacific and Austro-Malayan Islands, except Celebes and Papua; Lasionys (1 sp.) Guinea; Acanthomys (5-6 sp.) Africa, India and N. Australia; Cricetomys (1 sp.) Tropical Africa; Saccostomus (2 sp.) Mozambique; Cricetus (9 sp.) Palaearctic region and Egypt; Cricetulus (1 sp., Milne-Edwards, 1870) Pekin; Pseudomys (1 sp.) Australia; Hapalotis (13 sp.) Australia ; Phloeomys (1 sp.) Philippines; Platacanthomys (1 sp., Blyth, 1865) Malabar; Dendromys (2 sp.) S. Africa; Nesomys (1 sp. Peters, 1870) Madagascar ; Steatomys (2 sp.) N. and S. Africa; Pelomys (1 sp.) Mozambique; Reithrodon (9 sp.) N. America, Lat. 29° to Mexico, and south to Tierra del Fuego; Acodon (1 sp.) Peru; Myaomys (1 sp.) Guatemala; Hesperomys (90 sp.) North and South America; Holochilus (4 sp.) South America; Oxymycterus (4 sp.) Brazil and La Plata; Neotoma (6 sp.) U.S., East coast to California; Sigmodon (2 sp.) Southern United States; Drymomys (1 sp.) Peru; Neotomys (2 sp.) S. America; Otomys (6 sp.) S. and E. Africa; Meriones = Gerbillus (20-30 sp.) Egypt, Central Asia, India, Africa; Rhombomys (6 sp.) S. E. Europe, N. Africa, Central Asia; Malacothria: (2 sp.) South Africa; Mystromys (1 sp.) South Africa; Psammomys (1 sp.) Egypt ; Spalacomys (1 sp.) India ; Sminthus (1-3 sp.) East Europe, Tartary, Siberia; Hydromys (5 sp.) Australia and Tasmania; Hypogeomys (1 sp., Grandidier, 1870) Madagascar; Brachytarsomys (1 sp., Günther, 1874) Madagascar; Fiber (2 sp.) N. America to Mexico; Arvicola (50 sp.) Europe to Asia Minor, North Asia, Himalayas, Temp. N. America; Cuniculus (1 sp.) N. E. Europe, Siberia, Greenland, Arctic America; Myodes (4 sp.) Europe, Siberia, Arctic America, and Northern United States; Myospalaa: = Siphneus (2 sp.) Altai Mountains and N. China"; Lophiomys (1 sp.) S. Arabia, and N. E. Africa; Echiothria, (1 sp.) Australia. - . Eastinct Muridae.—Species of Mus, Cricetus, Arvicola, and Myodes, occur in the Post-Pliocene deposits of Europe; Arvicola, Meriones, and the extinct genus Cricetodon, with some others, in the Miocene. In North America, Fiber, Arvicola, and Neotoma, occur in caves; an extinct genus, Eumys, in the Upper Miocene of Dakota, and another, Mysops, in the Eocene of Wyoming. In South America Mus, or more probably Hesperomys, is abundant in Brazilian caverns, and Owymycterus in the Pliocene of La Plata; while Arvicola is said to have occurred both in the Pliocene and Eocene deposits of the same country.
* Myospalax has hitherto formed part of the next family, Spalacidae; but a recent examination of its anatomy by M. Milne-Edwards shows that it belongs to the Muridae, and comes near Arvicola.
The Spalacidae, or mole-rats, have a straggling distribution over the Old World continents. They are found over nearly the whole of Africa, but only in the South-east of Europe, and West of Temperate Asia, but appearing again in North India, Malacca, and South China. Ellobius (1 sp.), is found in South Russia and South-west Siberia; Spalaa (1 sp.), Southern Russia, West Asia, Hungary, Moldavia, and Greece (Plate II., vol. i. p. 218); Rhizomys (6 sp.), Abyssinia, North India, Malacca, South China; Heterocephalus (1 sp.), Abyssinia; Bathyerges (= Orycterus 1 sp.), South Africa; Georychus (6 sp.), South, Central, and East Africa; Heliophobus (1 sp.), Mozambique.
The Jerboas, or jumping mice, are especially characteristic of the regions about the eastern extremity of the Mediterranean, being found in South Russia, the Caspian district, Arabia, Egypt, WoL. II—16
and Abyssinia; but they also extend over a large part of Africa, and eastward to India; while isolated forms occur in North America, and the Cape of Good Hope. Dipus = Gerbillus (20 sp.), inhabits North and Central Africa, South-East Europe, and across Temperate Asia to North China, also Afghanistan, India, and Ceylon; Pedetes (1 sp.), South Africa to Mozambique and Angola; Jaculus = Meriones (1 sp.), North America, from Nova Scotia and Canada, south to Pennsylvania and west to California and British Columbia (Plate XX., vol. ii. p. 135). Eactinct Dipodidae.—Dipus occurs fossil in the Miocene of the Alps; and an extinct genus, Issiodromys, said to be allied to Pedetes of the Cape of Good Hope, is from the Pliocene formations of Auvergne in France.
The Dormice (Myocus), are small rodents found over all the temperate parts of the Palaearctic region, from Britain to Japan; and also over most parts of Africa to the Cape, but wanting in India. Some of the African species have been separated under the name of Graphidurus, while those of Europe and Asia form the sub-genera Glis, Muscardinus, and Eliomys. Eatinct Myosoidae.—Myocus ranges from the Post-pliocene of the Maltese caverns to the Miocene of Switzerland and the Upper Eocene of France; and an extinct genus Brachymys is found in the Miocene of Central Europe.
The Saccomyidae, or pouched rats, are almost wholly confined to our second Nearctic sub-region, comprising the Rocky Mountains and the elevated plains of Central North America. A few species range from this district as far as Hudson's Bay on the north, to South Carolina on the east, and to California on the west, while one genus, doubtfully placed here, goes south as far as Honduras and Trinidad. The group must therefore be considered to be pre-eminently characteristic of the Nearctic region. The genera are—Dipodomys (5 sp.), North Mexico, California, the east slope of the Rocky Mountains to the Columbia River, and one species in South Carolina; Perognathus (6 sp.), North Mexico, California, east slope of the Rocky Mountains to British Columbia; Thomomys (2 sp.), Upper Missouri, and Upper Columbia Rivers to Hudson's Bay; Geomys (5 sp.), North Mexico, and east slope of Rocky Mountains to Nebraska (Plate XIX, vol. ii. p. 129); 'Saccomys (1 sp.), North America, locality unknown; Heteromys (6 sp.), Mexico, Honduras, and Trinidad. Geomys and Thomomys constitute a separate family Geomyidae, of Professor Carus; but I follow Professor Lilljeborg, who has made a special study of the Order, in keeping them with this family. In the Post-Pliocene deposits of Illinois and Nebraska, remains of an existing species of Geomys have been found.