Birds of the Cayman Islands. 139 



riflge extends from Cape Cruz^ the most southerly point of 

 Cuba, right across this western division of the Caribbean Sea 

 into the Bay of Honduras. 



The major part of this ridge lies at a depth of 1000 

 fatlioms, but here and there along its length portions of it 

 have been upraised so that they are only some 500 fathoms 

 or less beneath the surface. On these last elevations or 

 plateaux appear still more elevated areas or banks, the 

 summits of which have attained to the level of the " plane 

 of the limiting line of sedimentation," or, in other words, to 

 the level at which reef-building coral organisms can flourish. 

 These reef-building organisms have been solely answerable 

 for the formation of the Caymans, which are purely coral 

 islands. In this respect, therefore, the Caymans differ from 

 all the other West Indian Islands except the Bahamas. 



Immediately to the south of the submarine ridge on which 

 the islands are situated, and between them and Jamaica, 

 there stretches a profoundly deep submarine valley known 

 as " Bartlett's Deep." The average depth of Bartlett's Deep 

 is 18,000 feet, but a long trough, which represents its deepest 

 part and wliich is situated, so to speak, at the very foot of the 

 stupendous range of which the Caymans form the summit, 

 has a depth of 22,000 feet. The water between Cayman 

 Brae and Cape Cruz, the nearest point of Cuba, attains to 

 a depth of 3000 feet. 



To all intents and purposes, then, so far as the avifauna 

 of the Caymans is concerned, we may look upon them as 

 pseudo-oceanic islands. They are obviously of very recent 

 origin, things of yesterday as compared with the other 

 Antillean Islands, and the only way in which they have 

 been " colonized " has been by the agency of wind and 

 marine currents. 



We should consequently not expect to find any very 

 marked changes of a specific character, still less of generic 

 importance, in the resident land-birds which characterize the 

 avifauna of the Caymans. Nor do we find such changes. It 

 is, however, remarkable how in many cases these resident 



