MID-ATLANTIC LAND BRIDGE 
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of North America. I explained this by the supposition that 
the widespread submergence of the Antilles destroyed most of 
the immigrants from Europe. It ought not to have affected 
the emigrants to Europe from the Antilles to the same extent, 
I mean those forms which spread from the Antillean centre, 
because they would have had more time to adapt themselves 
to the more elevated regions in the West Indies, and would 
thus have had more chance of surviving the submergence 
which did not entirely cover the islands. 
One of the most noteworthy examples of that kind, though 
not a very conspicuous onq, is the newt Spelerpes. 1 alluded 
to its range in North America on several occasions (pp.137— 
138 and p. 221), pointing out that its headquarters were in 
Mexico, while a single species had succeeded in reaching the 
Mediterranean region. We may assume, therefore, that 
certain members of the old American Spelerpes stock 
emigrated, in early Tertiary or even in Mesozoic times, by 
means of the trans-Atlantic land bridge, that extended from 
the Antilles to a land area which, covered part of the western 
Mediterranean (Fig. 14). That Spelerpes long ago existed all 
over the Antilles is indicated by the fact that a single species 
(Spelerpes infuscatus) still inhabits the island of Haiti. 
Another instance I alluded to (p. 173) in support of 
the mid-Atlantic land bridge theory, is the glass-snake 
family (Anguidae). The genus'Ophisaurus, which is found 
in the Mediterranean region, does not occur on the Antilles, 
but several species are known from the mainland of North 
America. The genus Anguis is quite confined to Europe, 
western Asia and north Africa. On the other hand, numerous 
relations live in the West Indies. Sauresia and Panolopus are 
confined to Haiti, whereas Celestus (Diploglossus) inhabits 
Portorico, Haiti, Jamaica, Cuba, Central America, Mexico 
and northern South America. The headquarters of the 
Anguidae certainly are in the West Indies and Central 
America, and it is from there that they must have spread to 
Europe and beyond, as far as the Himalayas, when a land 
bridge across the Atlantic permitted them to do so. 
Let us now return to the investigation of the geological 
history of the Antillean area. Among the vertebrates, the 
mammals perhaps are of the greatest importance, in so far 
