CAYO HUT I A AND THE REEF 57 



edge of the key disturbing many nesting birds we 

 rounded its northern end and struck out directly 

 for the reef some two hundred yards beyond. 

 Approaching this, the sandy bottom, at first soft 

 with grassy patches of Thalassa, becomes hard, 

 smooth, and dotted with gorgonians, sponges, 

 huge starfish, and quantities of short-spined sea- 

 urchins and many large holothurians. Occasional 

 small living coral heads (M&andra areolata) ap- 

 peared and an increasing amount of dead coral 

 blocks. About the edges of such patches of dead 

 reef rock waved many plumes of large branching 

 hydroids. We waded out cautiously to where the 

 water was breast deep. We were then upon the 

 inner edge of the main reef upon which any further 

 progress would have been difficult on account of 

 the rapidly increasing number of the long black- 

 spined sea urchins, the diademas (Centrochinus 

 setosum), and because of the increasing irregu- 

 larity of the bottom. Caverns opened to view 

 displaying floors of gleaming white sand and 

 literally swarming with fish. From holes and 

 crevices in the dark-colored rocks projected the 

 long antennas of the large spiny-lobster or crayfish 

 (Panulirus argus), and a general scuttling about 



