158 MAMMALS OF AMOORLAND. CHAP. ix. 



the British Isles, but still lives in the Seine, and is still more 

 abundant in the Loire. Another fresh-water univalve (Palu- 

 dina marginata Michaud), not British, but common in the 



Fig. 22 



Unio littoralis. Gray's Thurrock, Essex; extinct in British Isles, 

 living in France. 



south of France, likewise occurs, and a peculiar variety of 

 Gyclas amnica, which by some naturalists has been regarded 

 as a distinct species. With these, moreover, is found a peculiar 

 variety of Valvata piscinalis. 



If we consult Dr. Von Schrenck's account of the living 

 mammalia of Amoorland, lying between lat. 45 and 55 North, 

 we learn that, in that part of North -Eastern Asia recently 

 annexed to the Russian empire, no less than thirty-four out 

 of fifty-eight living quadrupeds are identical with European 

 species, while some of those which do not extend their range 

 to Europe are arctic, others tropical forms. The Bengal tiger 

 ranges northwards occasionally to lat. 52 North, where he 

 chiefly subsists on the flesh of the rein-deer, and the same 

 tiger abounds in lat. 48, to which the small tail-less hare or 

 pika, a polar resident, sometimes wanders southwards.* We 

 may readily conceive that the countries now drained by the 

 Thames, the Somme, and the Seine, were, in the post-pliocene 



* Mammalia of Amoorland, Natural History Keview, vol. i. p. 12, 1861. 



