Prof. P. M. Duncan on some Madrepararia. 363 



the only signs of its presence. But that there was plenty of sticky 

 ooze close by is e\d(ient ; for some was brought up by the appa- 

 ratus, 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 cemented to- 

 gether, 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 foraminiferal 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 Desmo- 

 phylla would place their calices far out of the way of matter col- 

 lecting 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 li\'ing 

 Ampliihelia brought up, and which was not growing on the cable, 

 contained no deposit, and that the dead Solenosmilia and a short 

 Caryopliyllia, neighbours to the form just noticed, had very small 

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

 worn by Aclilya penetrans and some 8pongida, are of themselves 

 sufficient to disprove a rapid rate of accumulation. The presence 

 of some most fragile outgrowths from the Lophohelian corals which 

 supported and partly enclosed the stems of some Hydroida contra- 

 indicate the existence of a current sufficient to move sticky ooze. 



It may be considered, then, that the deposit of minute sedi- 

 mentary matter and of pelagic Foraminifera is excessively slow in 

 its rate of accumulation 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 

 Glohujenna-ooze area will afford a corresponding observation ; 

 and we may assume that in the White and Red Chalks of England 

 the Madreporaria grew vastly more quickly than the deposit accumu- 

 lated which subsequently environed and overwhelmed them. One 

 of Lonsdale's discoveries was that of an Amphihelian-Xookmg mass 

 from the Chalk of Gravesend*; 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 Ked Chalk the corals are often \\idely 

 open and short and were probably very slow growers. All these 

 considerations tend to the impression that the chalk of old, what- 

 ever may have been its original nature, accumulated extremely 

 slowly. 



The variability of the specimens of Desmophyllum Crista-Galli 

 which were found on the cable is very great ; and in some instances 

 it is sufficient to permit of a specific distinction being made accord- 

 ing to the strict classilicatory rules. Doubtless had the specimens 



* Suppl. to Brit. Fobs. Corals, Cretaceous, Palaont. Soc. Uy P. M. Duiiean. 



