208 bulletin: museum of comparative zoology. 



lands than now exist, — probably in the region now covered by the 

 Pacific waters in the south, or the regions of the submerged Mosquito 

 and Eoncador banks to the north. The lay of the formations indicates 

 that the shore line was in the direction of the Pacific rather than the 

 Caribbean, and this one fact, together with other considerations, may 

 lead to the conclusion that land once existed off the Pacific side of Equa- 

 torial South America, and the submerged Mosquito banks did not then 

 exist in their present geographic outlines. 



But what was the source of these land derived sediments in the An- 

 tilles 1 At first it might be answered that the degradation of the Creta- 

 ceous volcanoes alone might account for this material ; but, although the 

 formation contains much volcanic material, it also has in it mica schists, 

 quartz, and other debris foreign to the composition of the Antillean 

 Cretaceous eruptions. Besides, the wide uniformity and assortment 

 cannot entirely be satisfied by this hypothesis. On the other hand, the 

 study of this material, considered from any point of view, suggests the 

 hypothesis that the present Post-Cretaceous material was deposited 

 upon the margin of pre-existing land areas lying to the northward, of 

 which they were a part, including the south point of Florida, the 

 Bahama banks, all of which may have been remnants of the northern 

 part of the hypothetical AVindward Jurassic bridge or Archipelago, and 

 that these lands during this epoch were being base levelled and subse- 

 quently completely concealed by succeeding phenomena. 



The presence of this land-derived material in the fundamental Scotland 

 beds of the oceanic island of Barbados is indeed perplexing. The oldest 

 formations of this little island, standing solitary and alone in the Athmtic 

 Ocean, are clearly composed of the debris of a former land, of which there 

 is now no track or trace unless it be the deep submerged ridge extending 

 northward from South America. AVe search in vain the visible structure 

 of the adjacent Windward Islands over a hundred miles to the west- 

 ward, and separated by a deep submarine trough, for a solution, but can 

 establish no connection between them. The only hypotheses entertain- 

 able are that they were either derived from a land now submerged, which 

 constituted the eastern bank of the Windward platform, or from a penin- 

 sula which at that time may have extended out from the northeast corner 

 of South America. If the latter conclusion is tenable, may we not also 

 suppose that the Aves Island bank is also a relic of this old Cretaceous 

 AVindward land*? 



The early Eocene base-levelling was the beginning of initiation of a 

 subsidence which took place in the latter part of the Eocene and early 



