LAND REGIONS. 183 



They are very numerous in individuals, and unlike the species 

 of the United States, which occur mostly in moist, shaded wood- 

 lands, they are frequently found in exposed, sunn}^ situations. 

 The species are most numerous towards the southern boundary" 

 of the region, and in cold countries are few. 



About twent3^ species of land and fresh-water mollusca are 

 found in Iceland and the Faroe Islands. 127 species occur in 

 Great Britain ; two only of which Limneea involuta and Assiminea 

 Grayana, are peculiar to it. On the other hand several species 

 are introduced (not indigenous). A few European species not 

 now living in Great Britain, are found there as quaternary fossils ; 

 whilst some of the commonest living species are not found in the 

 quarternary, hence must have become British within compara- 

 tively^ recent times. 



The malacology of the northern, central and eastern portions 

 of France presents no particular features ; but in the neighbor- 

 hood of the Vosges, Jura and Alpine ranges occur a few Helices, 

 etc., belonging to mountainous regions. The southern and 

 western parts of France include a large infusion of the species 

 proper to the Mediterranean Province. The French quaternaries 

 tell the same tale of the extinction of some species and subsequent 

 introduction of others, as do those of Great Britain; among the 

 former is a special group of small Hydrobias, called Lartetia. 



The countries of the north of Europe contain approximately: 



Sweden, 136 species ; Norwa}^, 80 ; Lapland, 16 ; Finland, 75 ; 

 Denmark, 133. 



Helix hai'pa, Say, a minute American shell, is probably circum- 

 polar in distribution as it has been found in Labrador, British 

 America, Xorway, Sweden and Lapland. 



Germany possesses 248 species, of which 125 occur throughout 

 Europe. The vast plains of Northern Russia have a fauna 

 resembling that of Germany, 



Siberian Suhregion. In 1877, Westerlund enumerated 137 

 species, of which 48 are terrestrial and 89 fluviatile. A number 

 of these are European species, several of them circumboreal ; 

 such as Vitrina pellucida, Helix pulchella, Gionella lubrica, 

 Pupa viuscorum, Physa hypnorum, Linneea auricularia , L. 

 palustrii^, L. stagnalis, Planorhis albus, Margaritana margariti- 

 fera, all of which recur in British North America and the northern 

 parts of the United States. ■ 



Tliere are a dozen or twenty special forms in Siberia, but they 

 are mostl}^ of European aspect, and in some cases are not really 

 distinct from European species. In Lalve Baikal, however, is a 

 special fauna, one of the most distinctive in existence ; it is 

 characterized by a number of genera related to Hydrobia (repre- 

 sented in the Colorado Desert of N. America by the peculiar 

 genus Tryouia), Choanomphalus (related to the Califoruian 



