334 



SOUTH AFRICA— ST. HELENA 



CHAP. 



form with a continuous peristome, perhaps akin to Bulimus ; 

 Apera, a form of slug ; and Ooeliaxis, a genus perhaps akin to 

 the Papuan and Queensland Perrieria^ are all peculiar. The 

 land operculates, which are not numerous, are of the East 

 African type. 



Land Mollusca of the 8. African Suh-region 



St. Helena. — The Molluscan fauna of St. Helena is perhaps 

 the most puzzling, as regards its geographical affinities, of any in 

 the world. It consists of 29 peculiar species of land Mollusca 

 (fresh- water species being unknown), 19 of which are recently 

 extinct, partly owing to the destruction of the forest, but are 

 found in considerable abundance in a state of good preservation. ^ 

 The genera are — 



Hyalinia . 1 



Patula . . 4 (3 extinct) 



EndodontalO (7 extinct) 



Bulimulus . 7 (5 extinct) Pupa . . 2 (extinct) 

 Pachyotus . 1 (extinct) Succinea 3 

 Tomigerus (?) 1 (extinct) 



The 5 genera which concentrate our attention are Patula^ 

 Endodonta^ Pachyotus (Fig. 222), Tomigerus., and Bulimulus., all 

 of which appear utterly strange to an oceanic island in the middle 

 of the S. Atlantic. Patula and Endodonta are essentially Poly- 

 nesian forms, occurring abundantly on all the island groups in 

 the Central Pacific. Pachyotus., Tomigerus (assuming its correct 

 identification), and Bulimulus are all S. American forms, the two 

 former being especially characteristic of Brazil. How this mix- 

 ture of genera now confined to regions so widely distant, not only 

 from St. Helena itself, but from one another, became associated 

 here, is a problem obviously not easy of solution. The fauna 

 is probably a remnant of a very ancient type, possibly at one 



1 Nine species have been introduced : 6 from Europe, 2 from the West Indies, 

 1 from the Western Isles. 



