14 THREE CRUISES OF THE " BLAKE." 



and Gorgonise, and the accompanying Comatulse and Ophiuridse, 

 living in such numbers on the windward coast of St. Vincent. 



We may contrast, again, the deep-water fauna off the Tortu- 

 gas, in the coral ooze, mainly made up of a most characteristic 

 association of fishes and Crustacea, with the hauls in deep water 

 at special localities, consisting entirely of thousands of specimens 

 of single species, either of ophiurans, or of sea-urchins, or of 

 feather-stars, or of crustaceans, or of gorgonians. 



Take again the bottom around the ridges between the West 

 India Islands, or that along the course of the Gulf Stream off 

 the Carolinas, which are swept nearly clear of all animal life, 

 and compare their inhabitants with the rich and varied fauna of 

 the same depths upon the continental shelf farther north, and 

 along the western shelf of the Windward Islands, on the lee 

 side, in the Caribbean ; or compare these faunae in turn with 

 the mass of animal life, mainly composed of gorgonians and 

 calcareous and horny sponges, found upon the broad plateau 

 on the west of Florida and on the Yucatan Bank ; there can be 

 no greater contrasts than those of the narrowly circumscribed 

 areas I have mentioned, where all the animals belong to the 

 West Indian fauna taken as a whole. This clearly indicates 

 radical faunal contrasts in very limited areas, which differ prin- 

 cipally in the character of the bottom, and where the physical 

 conditions, such as temperature, depending mainly upon cur- 

 rents and winds, are in striking opposition within comparatively 

 moderate distances. 



But by far the most marked contrast is perhaps presented by 

 the reef fauna to that which immediately follows it towards 

 deeper water. None of the corals of the most abundant fami- 

 lies or species characteristic of the West Indian reefs extend to 

 any considerable depth, and simple corals, which form so large 

 a portion of the deep-sea fauna, are not represented at all in the 

 Florida reef fauna. It was on the slopes of the rocky plateau 

 stretching into deep water off the Florida reefs that Pourtales 

 first dredged the extraordinary assemblage of ancient animals 

 which constitute the continental fauna, succeeding in depth the 

 reef fauna just mentioned. The contrast between the littoral 

 fauna of the tropics and that of the continental and abyssal 



