6 BULLETIN 354, U. S. DEPARTMENT OF AGRICULTURE. 



south side of the island in the valley of the Guanajibos at Sabana 

 Grande, and on the north side at the junction of the Don Alonso (or 

 Limon) and Arecibo Rivers. 



An uninterrupted block of limestone formation, known in places as 

 the Pepino Hills, 1 occurs along the north side of the island from Ciales 

 nearly to Aguadilla, and is some 6 to 10 miles wide from north to 

 south. It offers a marked contrast to the low rounded limestone 

 hills which flank it to the north, because of its greater elevation, 

 rough, angular topography, pitlike valleys, bare rock outcrops of 

 chalky whiteness, and subterranean drainage. Wherever the large 

 rivers, such as the Rio Grande de Arecibo and the Manati, cross this 

 area they have cut deep canyonlike valleys whose sheer cliffs of con- 

 siderable height occasionally rise directly from the water's edge. 

 Otherwise the area is strikingly devoid of surface drainage features. 

 The hills are very closely packed together, their connecting ridges 

 hardly more than rocky septums separating the disconnected pitlike 

 valleys. The steep-sided depressions show, on a tremendous scale, 

 to what an enormous extent rock solution takes place under tropical 

 conditions. 



The region, if viewed from above, would look like a honeycomb. 

 Not infrequently the "sinks" are 100 feet and occasionally 200 feet 

 or more deep. The larger pits sometimes contain an acre or more of 

 bottom with a very fertile soil, commonly under cultivation to such 

 crops as coffee, bananas, and ground provisions. The bottoms of 

 others are occupied by bogs or small lakes. The crags and summits 

 are almost invariably wooded. Caves, which mark the early stages 

 of pit formation, are common. 



Travel here is extremely difficult. Roads are out of the question 

 and the trails are not numerous and are extremely rough. There is 

 no alternative but to cross the pits in succession, descending to the 

 bottom of one and then climbing to the rim of the next almost 

 straight down and straight up again. 



THE COASTAL PLAIN. 



The sandy ridge fronting the coast forms a barrier between the sea 

 and a narrow low-lying area scarcely above tidewater level, and 

 partly marine and partly alluvial in origin. On the north side of 

 the island there are many swamps and lagoons covered with a thick 

 growth of mangrove bushes. The most typical are the Carlo y 

 Laguna de Tibufones between Arecibo and Barceloneta, Laguna del 

 Tortuguero north and east of Manati, and the string of lagoons east 

 of and connected with the harbor of San Juan. On the south side, 



1 The term "pepino" (cucumber) undoubtedly refers to the appearance of the elongated mamniillary 

 summits of the hills. An equally characteristic term, " cockpits," applied to a similar formation in Jamaica 

 is descriptive of the valley bottoms. 



