CHAP, v.] GENERAL CONCLUSIONS. 253 



exactly like it in any other species. We have freqnently seen 

 Glohigerina with spines, and the sarcode extended along them, 

 and displaying its characteristic movements; and on one or 

 two occasions we saw Pulmnulince with a half-contracted float, 

 resembling partially expanded bullae ; but in all these cases 

 jthe animals had been taken in the tow -net, and were greatly 

 injured. 



Everywhere in the globigerina ooze, Mr. Murray has de- 

 tected, in addition to the foraminifera which make up the 

 great part of its bulk, fragments of pumice, minute particles 

 of feldspar, particles and crystals of other minerals due to the 

 disintegration of volcanic rocks, such as sanidine, augite, horn- 

 blende, quartz, leucite, and magnetite, and rounded concretions 

 of a mixture of the peroxides of manganese and iron. 



I have already (vol. i., p. 212 et seq.) discussed very fully the 

 way in which, at depths over 2000 fathoms, the carbonate of 

 lime of the globigerina ooze is gradually removed, the ooze 

 becoming darker in color and effervescing less freely with 

 acids, until at length it gives place to a more or less homoge- 

 neous red clay ; and I have referred to the relative proportions 

 in which these two great formations occur in the Atlantic. 

 Their distribution may be broadly defined thus : the globige- 

 rina ooze covers the ridges and the elevated plateaus, and oc- 

 cupies a belt at depths down to 2000 fathoms round the shores 

 outside the belt of shore deposits ; and the red clay covers the 

 floor of the deep depressions, the eastern, the north-western, 

 and the south-western basins. An intermediate band of what 

 we have called gray ooze occurs in the Atlantic at depths aver- 

 aging perhaps from 2100 to 2300 fathoms. 



Over the red -clay area, as might have been expected from 

 the mode of formation of the red clay, the pieces of pumice 

 and the recognizable mineral fragments were found in greater 

 abundance ; for there deposition takes place much more slowly, 

 and foreign bodies are less readily overwhelmed and masked ; 



