SNAILS OF CAPE REGION 209 



of this genus of large snails are peculiar to the Cape Region, 

 several others being identical with Mexican ones. Some of 

 them have spread along the peninsula northward, yet it 

 seems certain that the Lower Californian centre of dispersal 

 lies in the Cape district, for no species occurs in California 

 proper. If we examine the range of the genus Bulimulus as a 

 whole, we find that its headquarters are in the West Indies. 

 From there it has travelled to eastern South America possibly 

 across a very ancient land surface. Another branch has gone 

 westward and populated the distant Galapagos islands. A 

 third stream apparently invaded the coast lands of South 

 America from the west, for we find numerous groups of Buli- 

 muli in certain western areas in Bolivia, Peru and Chile. 

 Still another section has struck directly westward across 

 southern Mexico to the southern parts of Lower California. 

 A couple of species have passed into Texas and further 

 east from this Mexican centre. 



Considering that the closely related genus Placostylus 

 inhabits New Zealand, as well as a series of archipelagoes 

 between it and the Solomon Islands, it must be admitted that 

 in Bulimulus we have to deal with an almost archaic genus, 

 and that the land-masses and islands on which it is now found 

 are probably fragments of ancient continuous lands. Acci- 

 dental dispersal of shells has formed the subject of Mr. 

 Medley's * special study. Yet he shows that the species, par- 

 ticularly of the southern Placostylus, being heavy massive 

 shells, are singularly unfitted for crossing distant seas by 

 occasional means of dispersal. Hence he arrives at the con- 

 clusion that the Solomon and Fiji islands, the New Hebrides, 

 Loyalty Islands, New Caledonia, Norfolk Island, Lord Howe 

 Island and New Zealand form a zoological province, and are 

 to be considered as the fragments of a shattered continent. 



A similar argument might be applied to Bulimulus, which is 

 so closely related to Placostylus. It seems permissible to 

 argue that the West Indies in early Mesozoic times were a 

 large united land-mass, that the latter was continued south- 

 eastward so as to join the archaic lands of eastern Brazil, that 

 it swept westward across what is now Central America out 

 * Hedley, 0., " Placostylus," A Study in Ancient Geography, pp. 337 

 339. 



L.A. P 



