190 LAND REGTONS. 



few acclimated European species, and are of 10 species only ; 

 but as many additional species are found as dead shells only, 

 rarely retaining their color and translucency. They are found 

 beneath the surface soil in the sides of ravines worn by the 

 heavy rains, at a height of 1200 to 1700 feet. " Their extinction 

 has probabh^ been caused by the entire destruction of the woods, 

 and the consequent loss of food and shelter, which occurred 

 during the early part of the last century" (Darwin's Journal, 

 488). Of the dead shells thus found, the only species which still 

 survives is Succinea Bensoniamo.. Among the extinct species are 

 7 Bulimus, including the curious B. aianxvulpina, and belonging 

 to two groups, both special to the island. The Helices appertain 

 to Endodonta, a Polynesian group. Three species of Succinea 

 form the special group Helisiga, and live in high parts, on the 

 leaves of arborescent compositse. Thus the ensemble of char- 

 acters of the molluscous fauna is original, and shows that St. 

 Helena has been insulated since a ver}'^ early period. 



Ascension Island, 800 miles N. W. of St. Helena, is not known 

 to possess an}^ molluscous inhabitants, except a slug, Limax 

 Ascensio?iis. 



9. South African or Cape Region. 



About 100 species have been collected in this region. The 

 genus Helix is very abundant, contrasting with the scarcity of 

 heliciform shells in intertropical Africa. The Helices belong to 

 two t3q3es, Dorcasia 5 sp. ; Pella 10 sp.; and there is also the large 

 diaphanous Helix Gajfra^the mollusk of whicli is carnivorous, and 

 is made the type of the genus ^rope. There are 11 sp. of 

 Achatina and 12 of Ennea, and a few Cyclostomidte, 4 XJnionidse. 

 The genera Physopsis, Isidoi'a and Spatha are also represented, 

 as throughout Africa. 



10. Malgachian Region. 



This includes, besides Madagascar, the islands of Bourbon, 

 Mauritius, Rodriguez, the Comoros and Seychelles. Whilst the 

 specific forms are peculiar to each island, the genera are common 

 to all and thus unite them into a single malacological province. 

 We find here a large develSpment of carnivorous species having 

 pupiform shells, Ennea, Gibbus; and the Cyclostomid^e are 

 predominant, attaining their greatest representation in Mada- 

 gascar, where many of them are spirally ridged (Tropidophora . 

 There is only one Helicina, at the Sej^chelles. 



In Madagascar there are more than 150 species of terrestrial 

 and fluviatile mollusks. The Helices, 15 in number, are beau- 

 tiful, and mostly belong to the genera Helicophanta and 

 Ampellita : one of them H. viridis is a Cochlostyla — a Philippine 

 Island group. There are 47 species of Cyclostoma, 13 Neritina, 



