260 MAMMALS. 



but we can laardly trust to it, for Baii'd, on the other hand, says that the Old-Workl species is 

 the largest ; " in fact, fully twice the size." In truth, there seems to be little on which to 

 found a species beyond size, colour, and length of tail — in other words, in those Tery characters 

 in which ordinary variation chiefly occurs. But here the important point is, that the distinctive 

 peculiarities on these points seem to be constant on each side of the Pacific. Similar constant 

 differences, however, occur between the individuals in different districts elsewhere. Baird noticed 

 them in all the specimens of Tamias quadbivittatus from a particular district in North America. 

 He saj^s, " In all the sfiecimens from the Upper ISIissouri and Yellowstone Rivers there is a constant 

 difference from the preceding description, in the much greater lightness of colour. The dark stripes 

 have much less black in them, &c. These are smaUer, and the tail longer. The tail is also much 

 lighter-coloured," &c. &c.* 



The difference in the proportions of these Yellowstone River specimens too is of the same character 

 as in those of the Siberian sjjccimens of Sperjiophilus Parryi, as well as of Tamias Pallasii. 

 Increase of size is accompanied with shortening of the tail, and diminution of size with an increase 

 in its length. It is as if the tail remained the same, and seemed only relatively longer or shorter 

 according to the increase or diminution of size in the other parts of the body. It would be 

 interesting, by a series of measurements both of Old-world and New-world individuals, to ascertain 

 ■whether this is the case ; and if so, where the increase really takes place. Those given by Dr. Baird 

 in his work sufficiently supply this for the American species ; all that is wanted is similar and equally 

 careful data for the Eiu'opean and Asiatic species. 



Spermophiltjs. (Map 88.). These Ground- Squirrels closely resemble ordinary Squirrels in appear- 

 ance, the easiest point of distinction being their possession of cheek-pouches. There are twenty 

 five species known, of which one is extinct and has left traces in the bone breccias of France and 

 Germany. Of the other two dozen, nine are Old-World (European and Siberian), and fifteen 

 North-American species. None are found to the south of the temperate latitiides of the northern 

 hemisphere. Those found in the Old World are chiefly Siberian : only two occur in Europe, 

 S. ciTiLLua in Austria, Huugarj-, Poland, Silesia, and Bohemia, and probably also in Russia and 

 Siberia; and S. guttatus in Volhynia, Bessarabia, and Russia between the Don and the Wolga. 

 The Ural, .^Utaic, Caucasian, and Kamtschatkan Mountains, the Irtisch and Kirghis Steppes, and 

 eastern Siberia, are the habitats of the .Asiatic species. 



In America a considerable number of species belong to a sub-genus proposed by Brandt 

 (Otospermophilus), with long ears, in contrast to the other species, which have very short ears. 

 These are not found in the Old World. None of the Spermophilcs of either section are met 

 with, or perhaps I should say, are now met with, on the eastern board of North America. Three 

 are found in the central districts, three in the Rocky Mountains, three in California, and five ia 

 Texas, Sonora, and New Mexico, and on the borders of Mexico. 



The most interesting of the Spermophilcs arc those known as S. Eversmanxi, and S. Parryi, 

 the former of which inhabits the eastern half of northern Siberia, from the Altaic Mountains to 

 Bhering's Straits, whore it meets the North American form, S. Parryi, which has as wide a range 

 eastward of the Straits, see Map 89. Brandt and the Russian zoologists generally consider these 

 species as identical. At the same time they can always be readily distinguished from each other, 

 S. Parryi being the larger of the two, and having a shorter and more bushy tail. 



* Baird, op. cit. p. 298. 



