80 ZOOLOGICAL GEOGRAPHY. [part m. 



conditions, of once wide-spread groups. If no wild species 

 of the genus Equus were now to be found, except in South 

 Africa (where they are still most abundant), and in South 

 Temperate America, where their fossil remains show us they did 

 exist not very long ago, what a strong fact it would have 

 appeared for the advocates of continental extensions ! Yet it 

 would have been due to no former union of the great southern 

 continents, but to the former extensive range of the family or 

 the genus to which the two isolated remnants belonged. And if 

 such an explanation will apply to the higher vertebrata, it is 

 still more likely to be applicable to similar cases occurring among 

 insects or moUusca, the genera of which we have every reason to 

 beheve to be usually much older than those of vertebrates. It 

 is. in these classes that examples of widely scattered allied 

 species most frequently occur ; and the facility with which they 

 are diffused under favourable conditions, renders any other 

 explanation than that here given altogether superfluous. 



The Solenodon is a member of an order of Mammalia of low 

 type (Insectivora) once very extensive and wide-spread, but 

 which has begun to die out, and which has left a number of 

 curious and isolated forms thinly scattered over three-fourths of 

 the globe. The occurrence, therefore, of an isolated remnant of 

 this order in the Antilles is not in itself remarkable ; and the 

 fact that the remainder of the family to which the Antillean 

 species belong has found a refuge in Madagascar, where it has 

 developed into several distinct types, does not afford the least 

 shred of argument on which to found a supposed independent 

 land connection between these two sets of islands. 



Summary of the Past History of the Neotropical Region. 



"We have already discussed this subject, both in our account 

 of extinct animals, and in various parts of the present chapter. 

 It is therefore only necessary here, briefly to review and sum- 

 marise the conclusions we have arrived at. 



The whole character of Neotropical zoology, whether as regards 

 its deficiencies or its speciahties, points to a long continuance 

 of isolation from the rest of the world, with a few very distant 



