Vol. 57.] PHrsiCAL DEVELOPMENT OF ANGUILLA, ETC. 533 



feet gave rise to a small amount of erosion, and the production of 

 shallow channels which can be traced across the great banks. 

 Then followed the sinking to a few feet below the present level, 

 allowing the accumulation of the marine earths, since raised a little 

 above the surface of the sea. Whether there is any terrestrial 

 movement in progress now is not known. 



YIII. Summary and Conclusions as to Changes of Level 

 OF Land and Sea. 



(1) The St. Martin plateau was a land-surface throughout the 

 long Miocene-Pliocene Period, during the earlier part of which it 

 appears to have stood 2500 feet or more above the present level, 

 and was probably connected with the now neighbouring insular 

 masses, from which it was disconnected by denudation during a 

 very long period of atmospheric activity, followed by subsidence, so 

 as to bring the present surfaces of the submarine banks to a level 

 so low that the undulating features of the base-level of erosion could 

 be formed on them ; for during the time when the deep and broad 

 depressions on the Antillean chain were being fashioned, the now 

 isolated island-groups stood out as table-mountains which were 

 slowly being eaten away by atmospheric agents. 



(2) A subsidence followed, of about 200 feet below the present 

 level, with the accumulation of the Point-Blanche gravels, and the 

 late limestones of Anguilla and Sombrero. Date about the close 

 of the Pliocene Period. 



(3) A re-elevation to 3000 feet as shown within the area, but in 

 reality much more (as found outside of this restricted area). The 

 epoch was characterized by the formation of great deep valleys 

 excavated out of the margins of the highlands, but the time was 

 not long enough for the recession of the gorges so as to dissect them 

 completely. It was during this early part of the Pleistocene 

 Period that the great rodents mentioned reached here from South 

 America, as Cope found that they were allied to South American 

 types of the Pleistocene Period, yet the race continued to live 

 sufficiently long to give rise to distinct species. It seems to have 

 survived until the region was again depressed and separated into 

 islets, or submerged, when they were finally extinguished. 



(4) The next submergence came in the mid-Pleistocene Period. 

 It carried the land 200 feet below the present level, with the 

 accumulation of the St. Martin gravels, etc. 



(5) The subsequent elevation was marked by moderate denudation, 

 with the production of shallow watercourses traceable across the 

 sunken banks, to depths of 150 or 180 feet. 



(6) Again there followed a moderate depression, so as to bring 

 the surface to a few feet below the present level, succeeded by a 

 rise of the low shell-bearing sands. 



Numerous as these changes of level may seem, the same 

 phenomena recur in the other islands, but the last minor movements 

 vary in different localities. 



