56 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



like those on Nassau and on other islands, in the shape of salt ponds. 

 The presence of Foraminifera in this marl, so like deep-sea ooze, yet 

 known to be formed only by the slow trituration of asolian rocks in very 

 shallow waters, raises the question of the depth at which Radiolarian 

 earth, as at the Barbados and elsewhere (Baracoa), may have been 

 formed. It is no more difficult to imagine that the formations round 

 the shores of such a shallow water lagoon have been elevated, than it is 

 to believe the same of an elevated coral reef. In the Billy Island marl 

 the presence of Lobulina and Globigerina would merely indicate that the 

 open sea had free access to the lagoon. Similarly, the Radiolaria of the 

 Barbados earth may have floated into the shallow waters in which it was 

 funned, were it not that the presence of Cystechinus, by analogy with 

 our recent species, indicates deep water. The marl of the shore of 

 Billy Island contained Lobulinse and Globigerinae, while the marl from 

 nearer the edge of the bank, in about four to five fathoms, and within 

 four miles south of Orange Cay, which contained a greater percentage of 

 coarse coral sand, also contained Lobulinse and Globigerinae, as well as 

 fragments of silicious Radiolarians. When within five miles from the 

 edge of the bank the bottom was quite clear of mud and marl, and was 

 composed mainly of nicely rounded particles of coral sand. 



From Orange Cay to Great Isaac. 



Plate I. ; Plate XII. Fig. 2 ; Plates XXIV. to XXVI. 



When approaching the western edge of the bank off the Racolas 

 Rocks to the south of Orange Cay, we began to see bars of corals in 

 from five to six fathoms of water. This had now become much clearer, 

 and, compared to the water on the midway of the bank, apparently car- 

 ried nothing in suspension. Still farther to the westward could be dis- 

 tinctly seen the dark blue line indicating the deep water of the Gulf 

 Stream off the edge of the bank. After passing the Racolas Rocks, we 

 came upon Orange Cay, a low ridge of seolian rocks absolutely bare, 

 pitted and honeycombed over its whole surface. Vessels crossing 

 the banks from Stirrup Cay sail an almost straight course from 

 there to Orange Cay, and next strike Salt Cay Bank, thus avoiding a 

 great part of the strength of the Gulf Stream, and making for Havana 

 from off Matanzas close to the north shore of Cuba. From Orange Cay 

 as far as Riding Rocks bars of corals run parallel to the edge of the 

 bank on an approximate north and south line. The corals on these 



