zxmong the Lesser Antilles steep banks slope down to considerable depths either di- 

 rectly from the shores, or from the edges of the supporting basis, sunk plateaus of 

 varying extent, usually in forty fathoms water. These banks exhibit within a limited 

 area a remarkable diversity in the conditions offered to animal life, resulting chiefly 

 from the rapid sinking of the temperature from the surface downwards. For, while the 

 littoral zone enjoys an average temperature of + 26 C., the bottom at 30U fathoms has 

 + 14 C., and at 600 fathoms the reading of the thermometer is not more than about 

 + 5C. 



Thus within a very restricted space a bottom is found, which exhibits in great 

 variety representatives of the different areas. Of course, these areas cannot be delined 

 by exact boundary lines. Many of the inhabitants of the cold zone have their out- 

 posts high up in the temperate regions and vice versa. The denizens of the warm zone 

 however seem to confine themselves to a limited range not reaching lower than 100 

 fathoms. In profusion of animal life this zone equals or even surpasses localities in other 

 seas which in this respect have become famous. Every spot is teeming with organisms, 

 from masses of Corallines invading and destroying all the vacant shells and calcareous 

 skeletons of every description, and transforming them into amorphous lumps and rocks, 

 to the powerful reef-building Madreporaria with their associated forests of Alcyonaria, 

 and their immense crowds of lodgers and parasites of Crustacea, Annelida, Mollusca, 

 Echiriodermata and Protozoa. But it should be borne in mind, that the common 

 dredge seldom affords proof of this abundance, which is hidden in the crevices and 

 tunnels of hard, dead coral-stems and incrustations of Corallines. When however a 

 more muddy and loose bottom is met with, the dredge often becomes choked to the 

 jaws with masses of specimens, particularly clusters of byssiferous Mollusca: Area, 

 Spondylus etc. sheltering an innumerable host of other Evertebrates. 



Already at from 90 to 150 fathoms a fauna begins to appear, the elements of 

 which are different from those of the littoral zone. Here the kingdom of brightly co- 

 loured Spongiaj displays its splendour of yellow, orange, red and brown, imparting 

 to most of their cohabitants a higher glow than is generally acquired even in the 

 zone above. This Spongia-zone is very narrow, often disappearing at 200 fathoms, 

 sometimes earlier, particularly where the bottom slopes more gradually and affords 

 more favourable conditions for the deposition of chalk-ooze, which appears in some 

 way to prejudice the growth of the coloured Spongiaj. 



