18 bulletin: museum of comparative zoology. 



The origin of this configuration, which is inextricably associated with 

 the stratigraphic history and geologic evolution of the island, will be 

 more fully explained in the later chapters of this report. 



The main mass of the island is an elevated region of rugose relief, 

 consisting of a nucleal mountain range surrounded by a high dissected 

 plateau. The higher region does not slope gradually to the sea, but is 

 terminated near the coast by very abruptly truncated bluffs, steep slopes 

 or benches, usually, but not everywhere, separated from the sea by a 

 narrow strip of plain, as if the original coast margins of the mountainous 

 upland once extended much farther seaward and had been horizontally 

 planed away by the sea's encroachment. The abrupt sea face of the 

 mountainous upland is a marked topographic peculiarity, which we shall 

 call the back coast border. This narrow ribbon of coastal plain is not a 

 continuous belt, but is interrupted, and constitutes an important feature 

 of the Jamaican topography. The secondary features are interior basins 

 and valleys in the summit of the plateau, certain coastal benches and 

 terraces carved out of the margin of the back coast border, and the 

 drainage valleys. 



Of these the interior mountains and the limestone plateau are by far 

 the most conspicuous features, and will be first discussed. 



The relation of the plateau region to the interior mountains is that of 

 an elongated mesa or bench completely surrounding a higher sierra, the 

 plateau having an outline somewhat like a child's bib, through the neck 

 of which the mountains of the east protrude, surrounded by a narrow 

 collar of plateau, while the main expanse or apron, which lies towards 

 the west, presents occasional views of the buried mountain structure, 

 through rents and holes made by water. The two types of relief of the 

 upland regions are readily distinguishable, even from a great distance, 

 by the entirely distinct physiognomy of their slopes. The interior moun- 

 tains are marked by deeply etched knife-edged salients (cuchillas) and 

 angular re-cntrants which present the aspect of a crumpled handker- 

 chief picked up by the middle, — an illustration used by Columbus in 

 describing the mountains of the Indies to Queen Isabella. These pe- 

 culiar escabradurato ^ slopes are shown in the illustrations on Plate VI. 

 The corrugations of the Blue Mountain Ixidge are plainly visible from 

 Kingston. On the other hand, the hills of the limestone plateau, 

 whether of peaked or flattened summits, present uncorrugated, densely 

 wooded slopes. 



^ From tlio Spiinish Kscnljrndura, signifying tlie erosion scratches, — "Bad- 

 land," relief of American usage. 



