286 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



is exemplified in many of the West -Indian Islands. As the coral 

 rock is usually harder than the rocks on which it rests, after its 

 emergence it protects the narrow exit behind which erosion is more 

 rapid and enlarges the basin. 



From the remarks already made it appears unnecessary to discuss 

 specially which are the older — the drainage basins occupied by the 

 harbors or the coral reefs now elevated about 30 feet. However, 

 that the Santiago basin is older than the coastal soborruco is shown 

 by finding the soborruco within the harbor mouth; and as I found 

 recent species of reef corals, apparently in place, on the east side of 

 Habana Harbor, south of the Morro, at a height of 30 feet above sea 

 level, the 30-foot reef seems to extend into the mouth of Habana 

 Harbor. The valleys are clearly older. On page 264 of this paper a 

 special point was made of the unconformity between the elevated 

 Pleistocene reefs and the underlying Miocene material and the in- 

 ference was drawn that the reefs were formed during subsidence after 

 erosion of the basement under them. This is precisely the interpreta- 

 tion Professor Davis had made of the relations in the elevated reefs 

 of the New Hebrides, but it seems such relations may develop in the 

 same cycle, and, in my opinion, they are of slight importance in their 

 bearing on the general theory of coral-reef formation. 



The Isle of Pines furnishes important information on changes in sea 

 level around Cuba. This island is nearly opposite Habana, 60 miles 

 south of the south coast of Cuba, from which it is separated by water 

 less than 10 fathoms deep. It comprises two parts, a southern which 

 is mostly swamp, and a northern which is topographically higher. 

 The surface of the northern division is mostly a plain, really a 

 peneplain (see pi. 72, fig. A), above whose surface stand monadnocks 

 of harder rocks (pi. 72, fig. B). This island is very different from 

 the main island for, as no Tertiary or Cretaceous marine deposits 

 are known to occur on it, it appears to have remained above sea 

 level during these periods, but it has experienced the later changes 

 of sea level which affected the larger island and during Pleistocene 

 time it was joined to Cuba. The peneplain was formed at a lower 

 level than that at which it now stands, it was then sufficiently uplifted 

 to permit streams to cut into it, and has then been depressed, 

 thereby drowning the mouths of the streams, but not bringing the 

 plain surface so low as it formerly stood (pi. 72, fig. C). The 

 coast line of the Isle of Pines and that of Cuba immediately north of 

 it both are indented by the embayment of stream mouths through 

 geologically recent submergence. 



That the Isle of Pines was joined to Cuba during Pleistocene time 

 is shown convincingly by its land fauna. Every species of reptile, 

 except one, found on it, Dr. L. Stejneger informs me, is known to 

 occur in Cuba, and two species of the mammalian genus Capromys 



