GKOGRAPHIC DISTRIBUTION. xlv 



as the Chinese H. binodata is to certain living and tertiary European 

 species. 



* * * 



Summary by Continents. The Americas are poor in autochthonous 

 types of Helices (and land snails generally), the genera Polygy ratio,, 

 Solaropsis and Macrocyclis being the only South American forms of 

 great antiquity, the genera Epiphragmophora, Pleurodonte and 

 probably Oxychona having been derived from the north in compara- 

 tively recent times, and the Amphidoxa forms are in all probability 

 stragglers from the Australian tract. 



The West Indies claim one group of genera, Sagda, Thysanophora 

 and Zaphysema of evidently great age and unknown ultimate affini- 

 ties, but the other elements, Pleurodonte, Cepalis and Polymita are 

 Mesozoic or early Eocene immigrants from the mainland, and 

 primarily from Asia. 



North America possessess in Polygyra, Polygyrella and Praticol- 

 ella a primitive fauna, to which has been added from Asia, the be- 

 logonous forms Vallonia, and the stock now differentiated into Epi- 

 phragmophora, Lysinoe, Glyptostoma and the West Indian genera 

 mentioned ; this addition can scarcely have been later than Creta- 

 ceous or base of the Eocene. 



Africa is in the north practically a part of Europe ; but at the 

 Cape a Helix-fauna of as primitive a type as that of eastern North 

 America is found, consisting of the genus Phasis of Endodontidce and 

 Dorcasia, a type allied to Polygyra, and probably a remnant of the 

 early wider distribution of the Protogona. S. Africa has real 

 affinities with Australia, but whether these are due to the preserva- 

 tion of antique types in both tracts, or to some actual connection, re- 

 mains to be solved. Madagascar is much more allied to Ceylon and 

 Australia than to S. Africa. 



Europe and western Asia. The western portion of Asia together 

 with Europe and North Africa, is peopled by a peculiar, highly 

 organized type of Helices practically confined to these regions, but 

 evidently derived ultimately from extreme south-east Asia or the 

 East Indies, by a Cretaceous (?) migration. 



Eastern Asia, from Japan and China southward to Australia,consti- 

 tutes another great division in Helix distribution, and the middle of 

 this area has been in all probability the birth-place of the groups 

 Epip hallo gona, Belogona and Macroogona. These three divisions 

 still occupy the region, various genera of the first, Camcena, Chloritis, 



