FAMILY COLIMACEA. 55 



tural analogy between them ; the hardened mucus, or epiphragm 

 as it is technically called, is broken away and renewed, as often 

 as the animal desires to crawl forth and again enclose itself. 



One-third of our land mollusks belong to this genus. Eleven 

 species occur throughout our islands, three nearly throughout, two 

 in the central and south parts, seven in the south only, and one in 

 the north only. As a general rule, the Helices increase in number 

 of species and individuals towards the south. All the twenty- four 

 species inhabit some or other of our southern counties, excepting 

 the minute H lamellata, which has not been collected in England 

 south of Scarborough. Four species, H. aspersa, arlustorum, ne- 

 moralis, and pomatia are pre-eminent in size, and in the colours 

 and development of their shell they are little surpassed in brilliancy, 

 considering the difference of latitude, by their analogues of the 

 intertropical islands of Eastern Asia. The last-mentioned, H po- 

 matia, is, however, local in Britain, and can hardly be said to be 

 indigenous. The next most conspicuous of our snails are H Can- 

 tiana, Carthusiana, Pisana, virgata, fasciolata, and ericetorum, 

 natives chiefly of the south and eastern maritime counties of the 

 chalk formation. Then we have a single lens-shaped species, H. 

 lapicida, belonging to a type which has its maximum of beauty 

 also in the Eastern Asiatic Islands. H. obvoluta is a solitary form 

 of doubtful British parentage, colonized within a very Limited area 

 in the county of Hampshire. The remaining half of the British 

 Helices are small species with thin horny shells, covered more or 

 less with a fibrous, often hairy, epidermis, dwelling in darker and 

 more concealed places of habitation, under stones or logs of wood, 

 among damp moss or decaying leaves. 



The range of our Helices in other parts of the world extends over 

 the chief part of Europe, and in some instances to a large portion 

 of Western Asia, between Siberia and Thibet. H. hispida, sericea, 

 fulva, pulcJiella and pygmcea appear in the list of Helices described 

 by G-erstfeldt from the district of the Amoor, and H. pulchella was 

 collected by Dr. Thomson on the north side of the western Hima- 

 layas. Southwards, our British Helices range in four instances to 

 North Africa, H aspersa, virgata, fasciolata, and rufescens, neither 

 of which are found in Northern or North-central Europe. Six species, 

 H. aspersa, Pisana, fulva, pulchella, aculeata, and pygmcea, appear 

 in the Azores, and three, H. Pisana, rufescens, and pulcJiella, in 

 Madeira and the Canary Islands ; but iu localities like Madeira, 

 which have a Helix fauna of their own, the presence of European 



