308 ORIGIN OF LIFE IN AMERICA 



and West Indies, the third in Mexico and the United 

 States. 



The two species of Vitrea (Hyalinia) seem to be related to 

 the Vitrea radiatula group, which, like Conulus, has a very 

 wide range in the Old World and the New. One of the Gala- 

 pagos species of Pupa is apparently found in Ecuador also, 

 the other is peculiar to the islands. The genus has a world- 

 wide range. All the species of Succinea, a genus which has 

 an enormous range, are confined to the islands. Tornatellina 

 chathamensis is closely related to the Hawaiian Achatellina 

 and belongs to a typically Polynesian genus. Helicina, as 

 already pointed out (pp. 157 158), has evidently invaded 

 America from the Pacific. Considering that it is an operculate 

 shell, and therefore supposed to be specially fitted for trans- 

 port across the sea by marine currents, it is surprising that 

 only a single species of Helicina should have taken advantage 

 of these facilities ('Compare Fig. 11). Lastly, one species of 

 Endodonta (E. helleri) has been observed on the archipelago. 

 Of the Galapagos mollusks this is one of the most in- 

 teresting, because the extremely primitive genus Endodonta 

 is almost confined to the Pacific region, including New Zea- 

 land, Tasmania, Australia, New Guinea and the Philippine 

 islands. Only St. Helena, where it is also found, lies entirely 

 outside the area. It is significant that not a single species is 

 known from the American or Asiatic mainlands or the West 

 Indies. 



I cannot help thinking that the attempt to derive the Gala- 

 pagos molluscan fauna from America is a mistake. The 

 family Bulimulidae is Pacific in origin, rather than American. 

 Succinea and Pupa have a wide range in the Pacific islands, 

 Tornatellina and Endodonta are altogether Pacific, being un- 

 known in America, Helicina is mainly Pacific, and it has 

 entered America from the west. Only Vitrea and Conulus may 

 be looked upon as typically American and Old World genera of 

 great antiquity. With their exception all the other genera 

 except two are more likely to have passed into America from 

 the direction of the Galapagos islands than vice versa. The 

 two others stopped short at the Galapagos archipelago and 

 went no further east. 



Too little is as yet known of the insects of the islands and 



