282 CHAPTER III 



p. 13). The genus occurs nowhere else on the earth, except in California (fig. 48), 

 where the Mount Lyell Salamander, H. platycephalus Camp., is restricted to the 

 BoreaJ zone of Sierra Nevada (Stebbins, 195 1, p. 146). 



The well-known genus Emys, among fresh-water Turtles, contains only two 

 species, orbicularis L. of Europe, North Africa and Hither Asia, and blandingi 

 Holbr., of central and eastern North America. 



During present conditions a dispersal across the Atlantic of these Vertebrates, 

 unable to endure salt water, is out of the question, except with the aid of man, 

 and this again would be an absurd idea since in no case the same, only related 

 species occur on both sides. 



Similar instances of related, but not identical, animals of a southerly Amphiat- 

 lantic distribution are more numerous among Invertebrates but it is sufficient 

 to mention a few examples. 



Darlington (1934, p. 86-88) discovered and described two species of the Carabid 

 genus Perileptus, from Cuba and Jamaica, a most surprising event since this was 

 known as an entirely Old World genus and, moreover, the two species belonged 

 to the areolatus group, confined to Europe, North Africa and the Macaronesian 

 Islands; two further species were subsequently described from Hispaniola (Haiti) 

 and Puerto Rico (Darlington, 1935). A quite similar distribution is recorded for 

 the otherwise Old World Carabid genera Stylulus, with the species nasulus Schauf. 

 on the island of St. Thomas, and Lymnastis, with two species in Cuba and Guate- 

 mala. 



These cases were stressed by Jeannel (1937, p. 356 a.f.) as evidence of an earlier 

 land-connection between the West Indies and the Mediterranean region. Darling- 

 ton (1938) has strongly opposed this view. To his mind, all of them (or their 

 ancestors) have been carried across to America with the trade winds. Though this 

 may be true for Perileptus and Lymnastis, being constantly or (Lymnastis) individ- 

 ually long-winged, I cannot agree that this possibility exists for the flightless, 

 blind Stylulus, subterranean in habit. The almost constantly very restricted 

 distribution of the individual species of subterranean beetles, for instance in 

 the Alps, where there are often heavy "Fohn" -winds, shows that their powers of 

 dispersal are extremely poor. On the other hand, they are among the most difficult 

 insects to collect and I am quite convinced that the actual distribution of genera 

 and higher groups of subterranean Carabidae is known only in fragments. It 

 should also be observed that the single West Indian species of Stylulus hitherto 

 known belongs to a subgenus of its own. 



However, Darlington is certainly right in rejecting Jeannel's idea of land-con- 

 nection, and his suggestion that small flying Carabids may be carried by air currents 

 at high altitudes was strongly confirmed by the investigations of "aerial plankton" 



