FAMILY COLIMACEA. 57 



We come now to the inquiry, How is the Helix fauna represented 

 in other parts of the world ? Of all mollusks, whether terrestrial 

 or marine, the Helices are the most universally distributed over the 

 globe. Dr. PfeifFer catalogues upwards of two thousand species. 

 About seventeen hundred is the number whose specific value has 

 been tested by comparison, and of about fifteen hundred of these 

 the habitats are known. It will be found that the Western Hemi- 

 sphere contributes three hundred and sixty species, representing 

 five natural provinces of distribution, the North American, West 

 Indian, Central American, South-west American, and Brazilian. 

 The Eastern Hemisphere contributes more than three times as 

 many, which, divided into five natural Provinces, may be classed 

 under the heads, Caucasian, Malayan, African, Australian, and 

 Polynesian. The Eastern assemblages of types, owing to the 

 more irregular configuration of the land, are of very unequal pro- 

 portions. The Malayan province, for example, which includes 

 the brilliant Molucca and Philippine species, is restricted to the 

 Eastern Asiatic islands, lying between Corea and Japan and the 

 Straits of Malacca. Islands like the Philippine group, and the 

 West Indies and Madeira, having a Helix fauna of their own, 

 abound in species. Allowing for the multiplication of names, it may 

 still be reckoned that the Philippine Islands have two hundred 

 species, the West Indies a hundred and fifty, and Madeira a hun- 

 dred, all emanating from their own respective areas of creation. 

 The British Islands have no Helix fauna of their own. Our four- 

 and-twenty Helices are outlying members of the great Caucasian 

 province, which includes five hundred and sixty species, spread over 

 Europe and Asia Minor to the Himalayas, and comprising Western 

 China and Hindoostan. The EngHsh Channel is probably some 

 impediment to the western march of the Caucasian snails. The 

 nearest continental land to Britain has twice as many species of 

 Helix; and they are equally numerous in the parts of Grermany 

 that come within the same isothermal latitude. 



The British Helices are : — 



1. aspersa. Shell large, imperforate, solid, of from four to four 



and a half whorls, blotched and banded with brown, lip ex- 

 pandedly reflected. 



2. pomatia. Shell very large, ventricose, with a half-covered 



umbilicus, of from four to four and a half whorls, fawn- 

 coloured, faintly banded, lip thinly dilated. 



