172 MATTHEW— RECENT DISCOVERIES OF 



3. Rodents of the Boromys group — 2-4 genera. 



4. Rodents of the Amhlyrhiza group — 3 genera. 



5. Nesophontes ] ...... 



^ ^ , , kwo very aberrant and primitive msectivores. 



o. 6olenoaon J 



These six groups constitute the surely native fauna. Most of 

 them are extinct; all of them except Solenodon are found as fossils. 

 Sixteen genera and about thirty-five species. 



There are various other mammals recorded as from one or an- 

 other West Indian island. Some of them are known to have been 

 introduced by man, others may have been. They are all species 

 identical or closely related with continental species. If any of these 

 were not introduced by man, they must have reached the islands in 

 comparatively recent times, geologically speaking, not earlier than 

 the Pleistocene, and some quite surely post-Columbian. Some are 

 found fossil, indeed, but never much altered by petrifaction, in the 

 uppermost levels of the cave and spring deposits. Such animals 

 as the European rats, domestic cat, domestic pig, etc., belong ob- 

 viously to post-Columbian time; the agoutis and armadillos of the 

 Windward Islands and other continental American species are 

 probably introduced by man, but they may not all be post-Columbian. 

 Such species as the Bahaman and Martinique raccoon, the Jamaica 

 rice rat, etc., described as distinct species, but certainly very closely 

 related to continental species, may also have been brought by man, 

 but long enough ago to have developed distinct races which have 

 been accorded the rank of species. Some may indeed have come 

 by natural means, and if so they can only have come through over- 

 seas drift, but for the present it is best to limit the discussion to the 

 purely native groups, all of which are genera, subfamilies or fami- 

 lies peculiar to the islands. 



The first group, the ground sloths, consists of four very distinct 

 genera allied to the Pliocene and Pleistocene North American Mcga- 

 lonyx and descended from the South American Miocene Eucho- 

 Iceops. No Megalonychidse are found in the South American Plio- 

 cene or Pleistocene ; they are replaced by more progressive and 

 specialized families. From th eevidence one may infer that they 

 reached the Antilles at the end of the Miocene or beginning of the 

 Pliocene, and that the four genera specialized there in adaptation 



