LAND REGIONS. 187 



4. Chinese Region. 



The conchological fauna of the North of China is palfearctic 

 in character, whilst that of the central and southern provinces 

 and of the islands is pahieotropical. There are a number of 

 special groups of Helices, such as Plectotropis, Acusta, Caniena, 

 JEgista, Gorilla, etc.; as well as a few Clausilia, Stenogyra and 

 Bulirainus. The more southern regions include some tropical 

 forms (of which a large proportion, as in tropical America, are 

 operculated). Among these may be named Streptaxis, Pupina, 

 Cyclotus, Diplomraatina, Cyclophorus, Al3^C8eus,Realia, Paxillus, 

 Helicina. The rivers are filled with magnificent species of Palu- 

 dina and Melauia, but fresh-water pulmonates are very few. 

 Bivalve mollusks of the Corbiculad?e and UnionidiB are very 

 numerous ; the species of the former numbering over 50, 

 exceeding in variety any other region ; whilst the Unionidag 

 (including the special group DipsaSi, are developed beyond any 

 region except that of North America — more than 100 species 

 being already known, although most of the streams have not 

 been thoroughly explored. 



5. Japanese Region. 



Nearly 200 species of land and fluviatile mollusks are known; 

 of which 73 belong to Helix and Hyalinia, 36 to Clausilia (several 

 gigantic forms — for the genus \ 23 are operculated, etc. The 

 Helicidse and operculates are of Chinese groups mostly ; there 

 are 8 species of Paludina, and 5 of Melania ; but the Unionidse, 

 so plentiful in China, are here scarce, numbering but a dozen 

 species ; there are 9 species of Corbiculadse. 



Several of the species of North Japan are of extensive 

 distribution : 



Helix {Hyalinia) nifida — rBurope. H (Hyalinia) minuiicula, 

 N. Am, 



Limnsea aui'icidaria and ovata, and Planorhia albus, Europe ; 

 Bythinea sfriatula., Amour ; Anodonta herculea and Margaritana 

 Dahurica, Siberia. 



6. Atlantic Region. 



The Azores, Canaries, Madeira and Cape Verd Islands contain 

 conchological faunas astonishing in their individuality. The 

 theory that these islands are the last vestiges of a vast Atlantic 

 continent is scarcely in accord with the distribution of their 

 shells, for not only are the species usually restricted to each 

 group, but even some of the generic groups are similarly 

 localized ; nor have these any relationship to the forms of the 

 African, European or American faunas. European species are 

 numerous, it is true, but they appear to have been accidentally 



