138 THE NEOG^IC REALM. [CHAP. 



from the Pliocene of Argentina a fact of importance as serving 

 to connect the Antillean fauna with that of the mainland. As 

 mentioned above, this genus belongs to a family (Castoroididce) 

 typified by the extinct Castoroides of the Plistocene of Ohio and 

 Georgia with species which rivalled a bear in point of size. The 

 other Antillean native mammals (exclusive of the bats, to which it 

 will be unnecessary to refer) are the two species of the genus 

 Solenodon respectively inhabiting Cuba and Hayti, and constitut- 

 ing by themselves a separate family among the Insectivora. It 

 has been already mentioned that the nearest allies of these strange 

 creatures are the tenrecs (Centetidce) of Madagascar; and thus both 

 are probably derived from unknown extinct insectivores formerly 

 inhabiting the northern hemisphere. As Jamaica and probably 

 several other of the West Indian islands contain large masses of 

 sedimentary deposits of Tertiary age, it is probable that they 

 come under the denomination of continental islands; and there 

 seems little doubt, from the evidence of their mammals alone, that 

 they have been connected with the mainland 1 . Dr Wallace is of 

 opinion that "originally they probably formed part of Central 

 America, and may have been united with Yucatan and Honduras 

 in one extensive tropical land. But their separation from the 

 continent took place at a remote period, and they have since been 

 broken up into numerous islands, which have probably undergone 

 much submergence in recent times. This has led to that poverty 

 of the higher forms of life, combined with the remarkable similarity 

 which now characterises them ; while their fauna still preserves a 

 sufficient resemblance to that of Central America to indicate its 

 origin." Recently, the connection of the West Indies with the 

 mainland has been worked out more fully by Mr J. W. Spencer 2 , 

 who, from observations made on the buried river channels so 

 numerous in some of the islands, concludes that there have been 

 several epochs of connection with the continent, one of which was 

 so late in date as the Plistocene epoch. The extinction in the 

 islands of the great majority of the mammals of the continent 

 is attributed to drowning. 



1 This is not the opinion of Dr A. Agassiz, who regards them as oceanic 

 islands. 



2 Geological Magazine, 1894, pp. 448 451. 



