380 CRINOIDAL MARBLE. 



coral limestone. The red shale was here all on one 

 side of it, none being seen lower down the river ; 

 while on the east side the trap appeared in the 

 bank, apparently between the shale and the coral 

 rock, overlying the former and capped by the lat- 

 ter. It certainly did not appear in any way to affect 

 or be connected with the coral rock, nor could I 

 any where trace its actual junction with the other 

 formation. The immediate banks of the river were 

 obscured, not only by the thickness of the vegetation, 

 but by huge masses of laminar and cellular traver- 

 tine, frequently as light as pumice-stone, and looking 

 like petrified froth : this was evidently deposited 

 partly by the river itself and partly from springs and 

 small water-courses, which probably derived their 

 carbonate of lime from the coral-limestone above. 

 I could not discover any organic remains in the 

 general mass of the shale or its embedded bands of 

 compact laminated limestone, but at one spot on the 

 east side of the river, just opposite the mouth of the 

 small lateral valley which comes down on the west 

 side, I found, to my great surprise, a block of cri- 

 noidal marble, precisely resembling that of Derby- 

 shire in every particular. This block was lying 

 partly embedded in the soil near a footpath, not far 

 from a hole that had been dug in the red shale. It was 

 a rudely cuboidal mass, about two feet every way. Its 

 lower part passed by insensible gradation into a fine- 

 grained laminated limestone, precisely resembling the 

 beds which were interstratified with the red shale; 



