AGASSIZ: BAHAMAS. 157 



which is the Serranilla Bank. It is somewhat circular in outhne, and 

 about twenty-four miles in greatest length. There is a general depth 

 of from five to fifteen fathoms upon it ; the bottom on the bank is coarse 

 coralline and coral sand. The bank is steep, the slope increasing rapidly 

 in depth from twenty to one hundred fathoms and more. On the east 

 face of the bank there are three small cays, from which extensive reefs 

 run along the eastern face more or less parallel with the 100 fathom 

 curve from Northeast Breaker to Beacon Cay. Farther south, east of 

 the Mosquito coast, are the Serrana and Roncador Banks to the east- 

 ward ; half-way between them and the Mosquito Bank comes the line of 

 the Quita Sueno Bank, of Old Providence, of St. Andrews, and of the 

 Courtown and Albuquerque Cays (Admiralty Charts Nos. 379, 1498, 

 Hydrographic Charts Nos. 373, 394). 



Both Old Providence (Hydrographic Charts Nos. 395, 1372, Admi- 

 ralty Chart No. 1334) and St. Andrews (Hydrographic Charts Nos. 391, 

 94.5, Admiralty Chart No. 1511) resemble in their general features, 

 but on a smaller scale, some of the volcanic Windward Islands, upon the 

 weather side of which coral reefs flourish. The greatest height of the 

 volcanic peaks of Old Providence is nearly twelve hundred feet ; from 

 the central peak's spurs run off terminating in shore peaks of from three 

 to seven hundred feet in height. Besides the main island, there are 

 upon its bank the small island of Santa Catalina and a couple of smaller 

 cays ; the bank carries from two to ten fathoms of water. A barrier 

 and fringing reef extends round the island, and a long reef stretches 

 out north. St. Andrews is only three hundred feet high. A few small 

 cays are scattered upon its bank ; its northeastern end is flanked by a 

 reef. Upon Courtown Bank (Hydrogaphic Charts Nos. 391, 945, Admi- 

 ralty Chart No. 1511) a barrier reef extends across it from the northern 

 end to within half a mile of the southern extremity. The noi'thern and 

 eastern sides of Albuquerque Cays Bank are skirted by a reef. 



The eastern face of Quita Sueiio Bank (Hydrographic Chart Nos. 394, 

 945) is flanked by a reef for twenty-five miles, leaving only a small part 

 of the bank clear at each end. The north and east edges of Roncador 

 Bank (Hydrographic Charts Nos. 373, 395, 945, 1374, Admiralty Chart 

 No. 1478) are fringed by a coral reef. The cays upon it are composed 

 of broken coral blocks and coral sand. 



The extreme east end of Serrana Bank presents a solid crescent-shaped 

 reef. The space within the horns is crowded with detached shoals, with 

 from five to ten fathoms alongside. The east face of the bank is abrupt, 

 no bottom at one hundred fathoms one quarter of a mile from the 10 

 fathom line J the south edge of the hank is edged by a reef. 



