The European, American and Asiatic Sciurinae are equally numerous, a large number of genera being now recognised. The typical genus, Sciurus, together with a number of New World genera, is distinguished by the large size of the baculum, which has a compressed terminal blade hollowed on the right side which carries below a downwardly directed process. The genera which have been grouped with the typical genus are Tenes, and all the American forms, except Tamiasciurus, the genus of Chickarees, or North American Red Squirrels, which on account of the suppres sion of the baculum is considered to represent a different group.
The North American Squirrels are a very numerous group, widely distributed across the continent, and in addition to those which belong to the typical subgenus, such as Sciurus (Sciurus) aureogaster from California, and S. (S.) poliopus from Mexico, and the genus Tamiasciurus, or Red Squirrels, referred to above, a large number of species and sub-species are placed in the genera Guerlinguetus and Baiosciurus.
The small American Squirrels, the Pigmy Tree Squirrels, from Central and South America may be regarded as represented by a distinct genus Microsciurus; the bodily size is much smaller than in the other American forms.
The remainder of the South American Squirrels may be included in 9 genera; Syntheosciurus, containing one species, S. brochus, from Panama; a small form with a narrow skull and long rostrum ; premolars mammae 6. Leptosciurus, a series of forms with short tails, from Colombia, Peru and Bolivia. Notiosciurus, a single small species, N. rhoadsi, is included in this genus; it comes from Ecuador, and possesses a narrow, short-nosed skull, and has the naked area on the hind feet much reduced. Mesosciurus, a large genus containing a number of different forms from the north ern part of South and Central America; the skull has a longer ros trum than in Guerlinguetus; p. mammae 6. In Hadriosciurus (p. mammae 8) the size is large and tail long and heavier than in Urosciurus. Urosciurus, the Giant South American Squirrels, contains a number of large species (head and body 35o mm.; tail 320 mm.), with long, broad tails; the coat is short and harsh, and the skull long and narrow. The species, which come from the Amazon basin, are highly coloured, being a mixture of orange and black. Simosciurus, from Ecuador and Peru, is similar
in size to Urosciurus but the tail is not so bushy or broad, and the pelage is longer and softer.
The Great-eared Squirrel of Borneo, Reithrosciurus macrotis, appears to be allied to the typical group; it is over two feet in length, half the length being occupied by a very large and bushy tail; the black ear-tufts are two inches long. The Giant Squirrels of Asia are grouped together in the genus Ratufa, the species being very numerous and some of them very strikingly coloured; they are found in India, Ceylon, Assam, Burma, Siam, Malay Peninsula, Sumatra, Java, Borneo, the Rhio Archipelago, east ward to the Natuna Islands and Celebes. A great variety of smaller forms is also found in Asia representing a number of different genera. Dremomys is a genus that contains some of the long-nosed Asiatic squirrels, inhabiting S. China and Formosa, Himalayas, Burma, Malay Peninsula and Borneo. A closely allied genus, also possessing a long snout, is Alenetes, from Burma, Siam and the Malay Peninsula, distinguished by its well-marked flank-stripes; species M. berdmorei. Allied to Menetes and the following genus is the Chinese Rupestes (R. forresti), a long-nosed genus with no small anterior premolar. In the Chinese Sciuro tamias the skull closely resembles that of Rupestes, but the col ouring is quite different, being yellowish-brown above and yellow ish-grey below, without the pale flank-stripe.
Lariscus is another genus belonging to this group ; about seven or eight different forms have been described from Borneo, Singa pore, Java, Sumatra, and the Malay Peninsula; distinguished by their shorter tails and by the presence of three dark dorsal stripes. Tomeutes is a widely distributed genus probably allied to Callos ciurus; a large number of species has been described, the best known of which is T. hippurus from the Malay Peninsula. The genus spreads from Nepal into China and east to Celebes and the Philippines. The genus Funambulus includes the well-known Palm Squirrels of India, which are confined to the Indian Peninsula and Ceylon; it is of interest to note that excluding the giant squirrels and flying squirrels no other form of squirrel occurs in the Penin sula.