FOSSIL VERTEBRATES IN THE WEST INDIES. 177 



tral America, but the eastern representatives may have come from 

 South America independently at an earlier date. Too few data to 

 go upon. (See addendum, p. i8i.) 



(c) The Boromys group, known as yet very imperfectly, appar- 

 ently limited to Cuba and Hayti. These also are quite distant from 

 any continental forms, suggesting. their having been isolated since 

 the Pliocene, but so far as we know this is not supported by diver- 

 sity of genera or insular specializations as among the ground sloths. 

 The relationship to this group of the Porto Rican Hetcropsomys is 

 in dispute, and it is well to defer conclusions. 



3. The insectivora are much more isolated than any of the pre- 

 ceding, but their relations are, although remotely, North American. 

 It is with the early Tertiary fauna of North America that their 

 apparent affinities lie. 



4. The giant tortoise has distant relations with the species of the 

 Galapagos islands, but has evidently been isolated and insular for a 

 long time, since the Miocene or early Pliocene, but not earlier than 

 that. The terrapin, on the other hand, is quite closely related to a 

 living species of the southeastern states and to a group of Pleisto- 

 cene species in the same region. It can hardly be supposed to be 

 older on the islands than the Pleistocene, especially since the sev- 

 eral islands in which it is found have not developed even distinct 

 subspecies, although there is a good deal of individual variation. 



5. The Cuban crocodile is common in the Pleistocene and prob- 

 ably reached the island somewhat earlier ; it is nearly related to a 

 Central American species, but it is quite as likely as not that that 

 species was more widespread in the Pliocene, perhaps through the 

 Southern States. (See addendum, p. 181.) 



6. Birds, bats, lizards, snakes, amphibians and fresh water 

 fishes, molluscs, insects and various other groups of invertebrates 

 are more widespread on the islands, as they are generally on oceanic 

 islands. I do not think the reason is so much their greater geologic 

 age as it is their greater facilities for dispersal, especially through 

 storms, as I have indicated. Generally speaking there are in each 

 group forms allied closely to modern mainland forms and others 

 which are more isolated, primitive and archaic in type, usually more 



PROG. AMER. PHIL. SOC, VOL. LVIH, L, JULY 25, I9I9. 



