The series of changes now suggested, will account for all the main features of the Antillean fauna in its relations to that of the American continent. There remains the affinity with Madagascar, indicated by _Solenodon_, and a few cases of African and Asiatic affinity in insects and land-shells; but these are far too scanty to call for any attempt at special explanation. Such cases of remote affinity and discontinuous distribution, occur in all the regions, and in almost every group of animals; and we look upon them almost all, as cases of survival, under favourable {80}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 mollusca, the genera of which we have every reason to believe 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 summarise the conclusions we have arrived at.