410 ORIGIN OF LIFE IN AMERICA 



(p. 120) that the mammals inhabiting Patagonia and south- 

 western North America in late Mesozoio and early Tertiary 

 times indicated the existence of a direct land bridge between 

 these two areas. But the Patagonian land-mass must have 

 included Chile or such parts of it- as were then above sea- 

 level. We know very little of the past fauna of Chile. It', 

 as I endeavour to prove, a portion of our living fauna is of 

 great antiquity, some animals snould reveal unmistakable 

 signs of this early affinity of Chile with that of south-western 

 North America. I imagine, as previously stated, that the early 

 Tertiary land bridge connected Chile directly with western 

 Mexico and California. Hence we might expect that not only 

 Chile and Patagonia, but the outlying islands of California, 

 as well as the Galapagos islands, ought to show a faunistic 

 relationship with one another. 



I have already alluded to the fact that three groups of the 

 snail Bulimulus inhabiting Chile and Peru, the Galapagos 

 islands and Lower California are very similar in their narrow 

 elongated shape, so that they were formerly considered to be 

 very closely related. Dr. Pilsbry* is now of opinion that this 

 similarity in appearance is not any evidence of near relation- 

 ship but a special parallel modification of different Bulimulus 

 stocks, or, as we might say, a case of convergence. He attri- 

 butes these cases to be products of similar environments. Yet 

 is the environment of Chile really so similar to that of the 

 Galapagos islands or Lower California ? Climatically and geo- 

 logically I should think there must be a good deal of difference 

 between these districts. 



The relationship between the western North American snail 

 fauna and that of western and south-western South America 

 is well illustrated by the distribution of the genus Epi- 

 phragmophora. This is a group of snails entirely confined to 

 Central America and the Pacific borders of North and South 

 America. It is important to note also that the majority of 

 the snails inhabiting the islands off the coast of California 

 belong to this genus. Cerros, Guadelupe, Santa Barbara, 

 San Clemente and other islands all have their peculiar species 

 of Epiphragmophora. Now the most interesting point about 



* Pilsbry, H. A., "Manual of Conchology (Pulmonata)," X., p. 126. 



