126 bulletin: museum of comparative zoology. 



which in many places is changed into extensive sand beaches. On the 

 mainland in the distance can be seen the outline of Mount Gunagua. 

 After passing Cay Coco, which only at Coco Point rises above the 

 first terrace, we sailed along a series of disconnected patches of reef 

 rock, the remnants of larger cays undoubtedly, like Cay Coco, Paredon 

 Grande, and the like. Along the face of Cay Guillermo are here and 

 there short stretches of low cliffs, parts of the first terrace, separated 

 by low rounded hills. The low hills of Triguano Island are now faints- 

 seen in the background. The plateau formed by the system of low 

 cays we are describing is widest in the region from Cay Verde to Cny 

 Frances. The terraces here were probably of great width, as the hills of 



PATCHES OF SOBORUCO, CAT FRANCES. 



older rocks upon which they flank do not in this part of Cuba come near 

 the coast line, as is the case from Santiago to Cape Maysi, and as far west 

 as Gibara. 



On the cays to the eastward of Santa Maria Cay, as far as Cay Frances, 

 the l'eef rock cliffs are separated by sandy beaches, and the hills are so 

 eroded that it is impossible to determine the terraces of which they once 

 formed a part. Upon the outer edge of the plateau, in from four to ten 

 fathoms of water, an extensive nearly unbroken reef runs from Nuevitas 

 to Cardenas, and is the source from which are formed the long sand 

 beaches that reach between the low cliffs of reef rock forming the sea 

 faces of the line of cays. There are patches of living corals often ex- 

 tending close to low-water mark, with heads awash at low tide. From 

 these sand beaches, exposed to the full force of the trade winds, patches 

 of recent seolian rock have occasionally formed on this line of cays. 

 Such a patch was observed at Cay Frances. The inner cays, many of 

 them extending toward the shores of the mainland, are composed of lime- 

 stone, and have been washed away below the level of the sea and con- 

 verted into regular mangrove islands. Cay Frances is really the first 

 break admitting vessels of any depth inside the cay reef plateau, and 

 forming a channel leading to the main passage running parallel to the 

 coast. Between this and Sagua there are two others, the principal and 

 deepest one leading to Sagua la Grande. 



