V. 



RELATIONS OF THE AMERICAN AND WEST INDIAN FAUNA AND 



FLORA. 



A GREAT number of animals and plants date back to a time 

 anterior to the present configuration of land and sea. In cer- 

 tain regions we are therefore justified in looking for traces of 

 ancient terrestrial or oceanic connections to explain the presence 

 of identical types at isolated points.^ 



The explorations of the " Blake," though primarily turned 

 toward the investigation of the ocean floor, had an incidental 

 bearing also upon these and similar problems. The work of 

 the " Blake " has added much to our knowledo^e of the former 

 connection between South America and the West India Islands, 

 and has taught us something also of the agencies which have 

 helped to determine their peculiar fauna and flora. Indeed, 

 hydrographic researches have given us the only acceptable 

 theory of the mode in which many oceanic islands have received 

 their present fauna and flora. 



According to Cleve,^ the oldest fossilif erous rocks of the West 

 Indies belong to the cretaceous, and were probably deposited in 

 a time of powerful volcanic action. Upon the highly disturbed 

 and metamorphosed cretaceous rocks are found almost hori- 

 zontal and undisturbed miocene beds. The eocene beds are 

 also to a certain extent metamorphosed, while the miocene 

 period must have been a period of long volcanic calm. The 

 position of the most recent pliocene and postpliocene beds seems 

 to indicate that some of the volcanoes now active in the West 

 Indies date back to the pliocene period, others to the postpli- 

 ocene. 



^ See Wallace's " Geographical Distri- - Kongl. Svensk. Vetensk. Akad. 

 bution of Animals," and his "Island Handl. Bdt. 9, No. 12. 1871. 

 Life." 



