THREE CRUISES OF THE / BLAKE." 
14 
and Gorgonis, and the accompanying Comatule and Ophiuridz, 
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 faune in turn with 
the mass of animal life, mainly composed of gorgonians and 
caleareous 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 Pourtalès 
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 
