50 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 23, 



length by four or five wide ; and they appear to be confusedly placed 

 one above another, with many ragged interstices and many smooth- 

 worn, rounded, large and small pits and subcylindrical cavities, some 

 of them pretty deep. The pyroxene, though it appears compact, 

 presents a multitude of small spaces, consisting of carbonate of Hme, 

 and many of these show minute structures similar to that of the fossil. 

 These masses of pyroxene may characterize a thickness of about 200 

 feet, and the interspaces among them are filled with a mixture of 

 serpentine and carbonate of lime. In general a sheet of pure dark- 

 green serpentine invests each mass of pyroxene, the thickness of 

 the serpentine, varying from the sixteenth of an inch to several 

 inches, rarely exceeding half a foot. This is followed in different 

 spots by parallel, waving, irregularly alternating plates of carbonate 

 of lime and serpentine, which become gradually finer as they recede 

 from the pyroxene, and occasionally occupy a total thickness of five 

 or six inches. These portions constitute the unbroken fossil, which 

 may sometimes spread over an area of about a square foot, or per- 

 haps more. Other parts, immediately on the outside of the sheet of 

 serpentine, are occupied with about the same thickness of what ap- 

 pear to be the ruins of the fossil, broken up into a more or less 

 granular mixture of calcspar and serpentine, the former still show- 

 ing minute structure ; and on the outside of the whole a similar mix- 

 ture appears to have been swept by currents and eddies into rudely 

 parallel and curviag layers, the mixture becoming gradually more 

 calcareous as it recedes from the pyroxene. Sometimes beds of lime- 

 stone of several feet in thickness, with the green serpentine more or 

 less aggregated into layers, and studded with isolated lumps of 

 pyroxene, are irregularly interstratified in the mass of rock ; and less 

 frequently there are met with lenticular patches of sandstone, or gra- 

 nular quartzite, of a foot in thickness and several yards in diameter, 

 holding in abundance small disseminated leaves of graphite. 



The general character of the rock connected with the fossil pro- 

 duces the impression that it is a great Foraminiferal reef, in which 

 the pyroxenic masses represent a more ancient portion, which having 

 died, and having become much broken up and much worn into cavities 

 and deep recesses, afforded a seat for a new growth of Foraminifera, 

 represented by the calcareo-serpentinous part. This in its turn be- 

 came broken up, leaving in some places uninjured portions of the 

 general form. The main difference between this Foraminiferal reef 

 and more recent coral-reefs seems to be that, while with the latter are 

 usually associated many shells and other organic remains, in the more 

 ancient one the only remains yet found are those of the animal 

 which bunt the reef. 



