1877.] Variability of some Madreporaria. 



135 



inappreciable on the cable during six years. A few Foraminifera in 

 crevices in the bases of a few specimens are the only signs of its presence. 

 But that there was plenty of sticky ooze close by is evident ; for some 

 was brought up by the apparatus, and it had got into parts of the calices 

 of some of the living corals. Moreover a mass of conglomerate which 

 was brought up, and which consisted of water-worn gneiss boulders ce- 

 mented together, had some of the mud entangled in it; and most of the 

 calices of the dead corals which were brought up at the same time, but 

 which were not attached to the cable, contained a small quantity of fo- 

 raminiferal and siliceous matter. 



It is possible that the motion of the tentacles and of the cilia of the 

 corals prevented the accumulation of sediment in their neighbourhood ; 

 but the tall peduncles of some of the Desmojohylla would place their 

 calices far out of the way of matter collecting on the base. Moreover 

 the part of the cable on which the coral grew may have been laid on 

 masses of stone above the level of the 'deposit. But the facts that the 

 calices of the living Am<phihelia brought up, and which was not growing 

 on the cable, contained no deposit, and that the dead Solenosmilia and a 

 short Caryophyllia, neighbours to the form just noticed, had very small 

 amounts in their calices, which had long been dead, and had been worn 

 by Achlya penetrans and some Spongida, are of themselves sufficient to 

 disprove a rapid rate of accumulation. The presence of some most fra- 

 gile outgrowths from the Lophohelian corals which supported and partly 

 enclosed the stems of some Hydroida contraindicate the existence of 

 a current sufficient to move sticky ooze. 



It may be considered, then, that the deposit of minute sedimentary 

 matter and of pelagic Poraminifera is excessively slow in its rate of accu- 

 mulation at 550 fathoms on this part of the Atlantic floor, and that it is 

 very much slower than the contemporaneous coral growth. 



An examination of some of the deep-sea corals of the true Globi- 

 gerina-oozQ area will afford a corresponding observation ; and we may 

 assume that in the White and B,ed Chalks of England the Madreporaria 

 grew vastly more quickly than the deposit accumulated which subsequently 

 environed and overwhelmed them. One of Lonsdale's discoveries was 

 that of an Amphihelian-looking mass from the Chalk of Gfravesend*; its 

 bulk was considerable, and yet many of the calices were close to the base, 

 and they were those of young buds. Again, in the Red Chalk the corals 

 are often widely open and short and were probably very slow growers. 

 All these considerations tend to the impression that the chalk of old, 

 whatever may have been its original nature, accumulated extremely slowly. 



The variability of the specimens of Desmophyllum Orista-Galli which 

 were found on the cable is very great ; and in some instances it is suffi- 

 cient to permit of a specific distinction being made according to the strict 

 classificatory rules. Doubtless had the specimens been separated, and 



* Suppl. to Brit. Fobs. Corals, Cretaceous, Palseont. Soc. By P. M. Duncan. 



