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 
