390 ORIGIN OF LIFE IN AMERICA 



chapter (p. 213), and that it might well form part of the 

 indigenous fauna of the island. There are twelve species, 

 some of which greatly resemble Polynesian forms, as Mr. 

 Smith pointed out, and, indeed, Dr. Pilsbry has placed them 

 provisionally with Endodonta, a genus otherwise confined to 

 Australia and Polynesia. There are three species of Succinea, 

 a genus which seems to be particularly unfit for transport 

 on drift-wood, while the most striking members of the snail- 

 fauna are a species of Bulimus, seven species of Bulimulus, 

 and one provisionally placed by Mr. Smith* in the South 

 American genus Tomigerus. 



More recently, Dr. Pilsbry demonstrated that these 

 apparently bulimoid snails are really members of the family 

 Achatinidae, and that they all belong to the genus Chilonopsis. 

 Since all the nearest relations of Chilonopsis are African, 

 genera, the affinity of this group is with Africa rather than 

 with South America. But the great antiquity of Chilonopsis 

 is indicated by the fact that Trichodina, to which it is closely 

 allied, has a most remarkably discontinuous range, occurring 

 only on some islands off the coast of West Africa and on the 

 Comoro islands in East Africa. Chilonopsis, moreover, is 

 more primitive than the genera of the large African Achati- 

 nidae, and Dr. Pilsbryf expresses the opinion that it, as well 

 as the related genera, originated from a common ancestor 

 which lived in Mesozoic times, when Africa and South 

 America were united by land. None of the species have any 

 affinity with South African ones, as was supposed to be the 

 case among the Hemiptera. 



Although Dr. White's Megarhaphis has now been shown 

 to belong to Macrorhaphis, a genus confined to Africa, 

 two species have since been taken in west Africa. 

 The supposed slight affinity of the St. Helena bugs to 

 those of the Cape has therefore entirely disappeared. As 

 regards the pronounced European element in the St. Helena 

 insect fauna, it is probably to a large extent of American 

 origin. The beetle Zophobas morio lives, outside St. Helena, 

 only in west Africa, Central and South America and 



* Smith, E. A., " Land-shells of St. Helena," pp. 259269. 

 t Pilsbry, H., " Manual of Conchology (Pulmonata) " (2), Vol. XVII., 

 pp. 171173. 



