86 I BULLETIN OF THE 



another, and with a .study of the inhabitants of shallower waters, and the 

 immediate seashore ; nor have the previous collections been made over 

 extensive areas, and so combined that every newly surveyed point was 

 determined with reference to earlier investigations, as was the case with 

 the dredgings of the last two years. In your recent surveys of the 

 Gulf, the dredging operations have been pursued over an area so large 

 as to preclude the possibility of any accidental and ill-considered conclu- 

 sions. 1 should not speak in such terms of investigations in which I 

 have had a share, bad not the main results been secured by M. Pour- 

 tales before I joined the cruise. 



There can be no doubt now that the area occupied by the reef 

 which rises to the surface of the ocean has a peculiar, independent 

 fauna, totally distinct from that of deeper waters. To this area belong 

 those species of corals known as the true builders of coral-reefs, and to 

 which, in a previous report to your predecessor, I gave, on that account, 

 the name of reef-builders. The range of this fauna in depth is very 

 limited ; it does not extend below ten fathoms, and is mainly occupied 

 by corals acquiring in their aggregate communities very large dimen- 

 sions, such as Madrepora palmata, cervicornis, and prolifera, Porites 

 astrceoides, Oculina diffusa, Eusmilia fastigiata, Astrcea annularis and 

 cavernosa, Tsophyllia dipsacea, Manicina areolata, Colpophyllia gyrosa, 

 Meandrina mammosa, and other species of the genus, Diploma, cere- 

 briformis, Siderastrcea radians and siderea, Agaricia agarieites, Myce- 

 dium elephantotus, Millepora alcicomis, the coarser and larger kinds 

 of Gorgonia, and a host of animals of all classes living in and upon the 

 reef, among which Rhipidigorgia flahellum, Diadema antillarum, and 

 Strombus gigas are the most conspicuous. From this region (the only 

 one of the kind which has been carefully surveyed by naturalists) I 

 formerly secured those large and beautiful collections of corals which 

 now adorn the Museum of Comparative Zoology. 



Beyond this area, the width of which varies along the coast of 

 Florida from a few miles, in (he neighborhood of Cape Florida, to 

 twelve, fifteen, or twenty miles and more oil' Cape Sable, we find 

 another zone, rather sterile, or at all events not marked by that rich- 

 ness of animal and vegetable lif»! which characterizes the reef range. 

 The bottom of this second zone is a muddy mass of dead and broken 

 shells, broken coral.-, and coarse coral-sand ; it is chiefly inhabited by 

 worms, and such shells as by their nature seek soil of this character, 



