258 SUMMARY OF DISTRIBUTION. 



and Cambojia, and in India as far northward and westward as Sik- 

 kim-Himalaya. Two remarkable land shells, amongst a charac- 

 teristic assemblage of others, collected lately in Cambojia, are con- 

 spicuous examples of species of the same typical character, sej>&- 

 rated by an intervening sea. Helix Cambojiensis is a species of 

 which the only other example of similar type, H. Broohei, occurs 

 in Borneo; and Bulimus Cambojiensis is of a type which appears 

 in Burmah in B. atricallosus, while both belong to a particular 

 specific type, B. citrinus, centred in the Moluccas, and not found 

 in the intervening Philippine Islands. In India Malayan forms 

 appear at the north-western confines of the province, among the 

 Nilgherry and Khasiah Hills, in the richly coloured Cyclophori, 

 intermingled with small Caucasian forms. 



One of the most remarkable instances of the types of one pro- 

 vince mingling with the types of another, appears in Siberia. 

 It was shown in ' Johnston's Physical Atlas,' published in 1852, 

 that the tiger ranges from India, as high up as the 50th parallel of 

 latitude, where the river is frozen over for at least six months in 

 the year. Mr. T. W. Atkinson during his travels in the Valley 

 of the Amoor, met with the tiger, lynx, and panther, in the Middle 

 region, almost as plentiful as in the jungles of Hindostan, mingling 

 in their distribution with British species, such as the fox and stag. 

 Every night, while encamping, fires were lighted to frighten away 

 the tigers. Having been led by this to examine the species of land 

 and freshwater mollusks of the Amoor, described by Gerstfeldt, I 

 was impressed with the same startling phenomenon. Paludina 

 Ussuriensis and Melania Amurensis, two singularly characteristic 

 species, of undoubted Malayan type, mingle with Caucasian species 

 (many of them British) in the isothermal latitude of Iceland, with- 

 in five degrees of the limit of permanent ground frost. 



