EIGENMANN: THE FRESHWATER FISHES OF BRITISH GUIANA 9 



undulating plateaus, with bold, and in some cases, perpendicular sandstone escarp- 

 ments, varying in height from about twelve hundred to over two thousand feet, 

 and eventually forming a large undulating table-land at an average height of about 

 thirty-five hundred feet above the sea-level. In many parts of the mountains and 

 table-lands great and deep gorges have been eroded by the rivers and streams 

 which traverse them. They attain their greatest height at Mount Roraima and 

 Mount Kukenaam, both of which rise over eight thousand five hundred feet above 

 the sea. The portion of this range which extends westward and down the southern 

 bank of the Mazaruni River to the vicinity of the Teboco Cataracts retains the 

 striking flat-topped features and is known as the Merume Mountains." 



"The elevated table-land (8635 feet) of Mount Roraima is about twelve square 

 miles in area, and on it the boundaries of the colony with those of Venezuela and 

 Brazil meet at a common point. This very remarkable mountain, together with 

 Mount Kukenaam, is a part of one of the most extensive sandstone formations 

 on the globe, and they both rise with perpendicular cliffs of sandstone two thousand 

 feet in height above the base of the surrounding country." 



"The highest plateaus, such as Mount Roraima, are mostly bare, exposed 

 expanses of rock, between the crevices of which grow many rare and curious orchids 

 and other flowering plants, besides some low bushes and extremely stunted trees." 



General Geology. 3 

 [p. 19.1 " The Coast-Lands. — The alluvial deposits are of considerable, but 

 unknown thickness. As they rest upon beds of pipe-clay or impure kaolin it is a 

 matter of great difficulty to decide whether the borings for underground waters, 

 which have from time to time been made in various parts of the coast-lands, have 

 been wholly in the alluvium, or have, as they certainly have done in some cases, 

 penetrated through these beds into the underlying residuary clays. In places, 

 however, the alluvial deposits have been proved for depths of over two hundred 

 feet, and it is possible that in many places their thickness far exceeds this. The 

 cores of the borings show that the alluvial deposits consist of beds of more or less 

 indurated marine muds and sands which have been laid down so as to form beds 

 of clay, of mixed clay and very fine siliceous sand, locally known as 'caddy.' and 

 of siliceous sands varying much in texture — some beds consisting of sand of ex- 

 tremely fine texture, others of coarser grain, while others again approach in char- 

 acter fine grits or gravels. In places some of the beds contain considerable quantities 



3 The notes upon the Geology are derived from the same work hitherto quoted, and from the pen of 

 Mr. J. B. Harrison, the Government Geologist of British Guiana. 



