208 ORIGIN OF LIFE IN AMERICA 



The flora of the Cape Eegion is sub-tropical, a considerable 

 proportion of the plants being West Indian. There are also a 

 few genera which do not occur elsewhere on the American 

 continent or the neighbouring islands. A small tree abun- 

 dant in the Cape district belongs to the genus Albizzia, which 

 is otherwise confined to Australia and the warmer parts of 

 Asia and Africa.* Although the lower Californian species is 

 quite distinct, its occurrence there might be attributed by 

 some naturalists to accidental distribution by marine currents 

 during some former period. No other occasional means 

 of transport could be thought of. But Albizzia is by no 

 means an isolated instance of floristic relationship between 

 the countries bordering the west and east sides of the Pacific 

 Ocean. Difficult problems of distribution of that nature are. 

 apt to be looked upon as instances of accidental dispersal. 

 Yet these puzzling cases of distribution often supply us with 

 valuable clues with reference to possible changes of land and 

 water that may have taken place. That the Cape Region of 

 Lower California is really a fragment of an ancient land -mass 

 is suggested by the occurrence there of the burrowing lizard 

 Euchirotes, of two species of the fresh -water oligochaet worm 

 Kerria, and by a good many other faunistic features. Kerria 

 is only met with in that region, in the West Indies and in 

 southern South America. 



Among the most interesting members of the Cape fauna 

 are the land shells of the genus Bulimulus above referred 

 to. Dr. Cooper, f in his series of valuable papers, only 

 mentions a few species found in that region, but he 

 alludes to the noteworthy fact that two of the Bulimuli 

 only live on the peninsula of Lower California, and in a similar 

 situation on the coast of southern South America, though quite 

 absent from the intervening moist tropical region. Dr. Dall,J 

 and more recently Dr. Pilsbry, have shown, however, that the 

 Cape species are not identical with the South American ones, 

 though extremely like them in general appearance, and that 

 they, together with those of southern Mexico and the interven- 

 ing islands, form a group by themselves. About twenty species 



* Brandegee, T. S., "Flora of Baja California," p. 222. 

 t Cooper, J. G-., " Molluscs of Lower California," p. 99. 

 t Ball, W. H., " Bulimulus in Lower California." 



