SOURCE OP ST. Peter's river. 37 



very compact in texture, but presenting at the same time 

 a slaty structure, and divisible in layers parallel to the stra- 

 tification. This limestone is replete with organic remains, 

 chiefly belonging to the Encrinite, Terebratula, Productus, 

 &c. among which we also found a shell belonging to the 

 genus Trochus or Turbo. These shells are very abundant 

 in the rock ; they are found, as far as we could judge, irre- 

 gularly disseminated, and adhering so closely that it is im- 

 possible to separate them, or to divide the mass into speci- 

 mens which shall exhibit their characters uninjured; but 

 being for the most part formed of calcspar, they resist de- 

 composition better than the compact limestone in which 

 they are imbedded, and from this circumstance the best 

 specimens are found protruding from the exposed surfaces 

 of the rock. 



This bed offered great interest to the two naturalists of 

 the expedition, the one as zoologist, the other as geologist. 

 Mr. Say thought he beheld in it the confirmation of an 

 opinion which he had long entertained, that, of all fossils, 

 the Encrinus is that which resists decomposition best. 

 Without pretending to dispute the correctness of the ob- 

 servation, as a general one, Mr. Keating thought that the 

 present instance did not confirm it, and that there were 

 many spots where the bivalves, (Terebratula and Productus,) 

 indicated a greater degree of hardness and solidity, by re- 

 sisting the effects of the weather better than the Encrini. 

 This we state as being perhaps the only time when the 

 two naturalists differed in their observation of the same 

 fact, when coming under the notice of both. 



Upon this limestone lay a bed of coal, of about two feet 

 in thickness, and apparently of a very good quality; some 

 works of no great amount were undertaken here not long 

 since, which are unattended to at present. We were told, 



