GEOGRAPHIC DISTRIBUTION. xll 



The South African genus Dorcasia, although so widely separated 

 geographically, seems to be a member of this group of genera. It 

 is probably a remnant of a large number of Protogona which may 

 have had a wide range in the Eastern Hemisphere in Mesozoic 

 times. 



Macroogona. This group comprises all the large Helices, in fact 

 all the Heliddw of Madagascar and the Seychelles, with genera in 

 Ceylon and Moluccas, and another group of genera in eastern 

 Australia and Tasmania (see page 148). No profitable speculations 

 can now be based upon this peculiar range, which probably dates 

 from Mesozoic time. The largest known Helices belong to this 

 group, as well as some very handsome forms, such as Acavus hcema- 

 stomus and Pyrochilus lampas, described in the last century. As a 

 temporary expedient, we have placed the N. Chilian group Macrocy- 

 clis here, but it may prove to belong elsewhere, possibly to Proto- 

 ; gona, when the genitalia come to be examined. 



Teleop hallo gona. As stated on p. 56, this group, consisting of 

 three genera only, is essentially West Indian. Zaphysema is re- 

 stricted to Jamaica ; Sagda is nearly as local, although a few species 

 from Hayti and Cuba are referred here ; while Thysanophora is 

 universally diffused throughout the West Indies, and occurs on the 

 mainland from Trinidad to Florida. 



Epiphallogona. The range of this group of genera includes Aus- 

 tralia (but not Tasmania), the Solomon Islands (but neither New 

 Caledonia or New Zealand), New Guinea north throughout the East 

 Indies, and the mainland of Asia from India to Japan. In Amer- 

 ica it covers the West Indies and northern South America. The 

 majority of genera and species are insular. 



Arising from an Oriental Protogonous stock now extinct, prob- 

 ably a remnant of the same which had much earlier given birth to 

 the Macroogona, this tribe seems to hav r e radiated in all directions. 

 There is no evidence showing that it ever extended further west than 

 at present; but in the north it evidently passed over a Bering 

 bridge, and travelled southward in America, becoming established 

 in the West Indies, probably in Secondary times. In this invasion 

 of American soil, the ancestors of the West Indian and Mexican 

 genera of Cyclostomatidw and Cyclophoridce probably shared, the 

 nearest allies of these groups being Oriental forms. 



Whether the American Clausilias accompanied this early exodus, 

 'Or a later one, remains uncertain ; and the same is true of the 



