FOSSIL VERTEBRATES IN THE WEST INDIES. 179 



any. The islands are not the remnants of a former Antillean con- 

 tinent ; on the contrary they have been built up, partly by uplifting- 

 and uptilting of blocks along fault-lines, partly through volcanic 

 eruptions, largely submarine, along the lines of weakness and fault- 

 ing. They are not very old geologically, the oldest known rock 

 being the marine Jurassic of western Cuba ; nearly all if not all of 

 the metamorphic rocks mapped by the U. S. Geological Survey as 

 Palaeozoic are either certainly or probably Cretaceous ; and the lesser 

 Antilles are the youngest geologically. A land connection with 

 Florida is practically forbidden by the geology ; a land connection 

 via the lesser Antilles is unlikely in the later Tertiary, and very un- 

 likely earlier ; a land connection via Hayti, Jamaica and Honduras 

 is unobjectionable, but there is no particular evidence in the geology 

 or submarine topography to show that there zvas such a connection 

 in the Tertiary. There is, however, considerable to indicate that 

 the relatively shallow banks that stretch eastward from Honduras 

 and Nicaragua almost to Jamaica may have been partly or wholly 

 out of water about the Pliocene or Pleistocene. In short, if a con- 

 tinental connection is required by the faunal evidence, this is by all 

 odds the most likely place for it. 



The second general consideration is the incomplete character of 

 the fauna. It is not a continental fauna, either North or South 

 American, but an insular fauna arisen from development in isola- 

 tion of a few individual elements of each. Such a fauna is not the 

 result of invasion from North or from South America over a con- 

 tinuous land area. Its incompleteness can no longer be ascribed to 

 extermination by man, for we see that the Pleistocene fauna, while 

 much more extensive, was obviously and significantly incomplete 

 and insular in type. It cannot be ascribed to scanty fossil material, 

 for we have now very large collections of both cave and spring fos- 

 sils. It cannot be ascribed to drowning out of the fauna, for we 

 have surviving on the islands two types of Insectivora that date 

 back to the middle or early Tertiary. 



A more particular examination of the different groups of mam= 

 mals, etc., confirms this general conclusion. The several groups 

 indicate derivation from different sources geographically, and at 

 different times geologically. If we insist upon the need of conti- 



