427 



evidence of its existence as far as the geological survey has yet 

 been made ; on the contrary, he finds the junction of the coarse 

 grit and the overlying slates above the Hudson River group per- 

 fect. He drew a section from St. Albans, on the lake, eastward, 

 showing the order of superposition of the rocks, which all have a 

 small dip, not more than 20°, and the position in which the 

 trilobites have been found. With regard to the Olenus discovered 

 there. Prof. Hall is inclined to consider it as belonging to a new 

 genus of trilobites. 



In reply to a question as to the age of the Braintree rock con- 

 taining Paradoxides, Prof. Rogers observed that the only in- 

 dication was to be derived from the fossils and their comparison 

 with the Primordial fauna of Bohemia. The age could not be 

 certainly pronounced upon, without accepting as a principle in 

 paleontology that fossils determine exactly the age of strata ; this 

 has many exceptions showing that the lines are not always pre- 

 cisely defined. He mentioned several instances in the Appala- 

 chian chain and elsewhere, where a mingling of fossils invalidates 

 the law of their strict limitation to determined strata. 



Mr. Marcou reiterated his belief in the supremacy of strati- 

 graphy in paleontology. He regarded the instances cited by Prof. 

 Rogers as exceptional, and as what occasionally is found the world 

 over on the edges of a basin, where great disturbance has evidently 

 taken place, mixing together fossils of different strata ; but he 

 denied that similar mixtures are ever found in the middle of a 

 basin. 



Dr. C. T. Jackson inquired if the Paradoxides of Braintree is 

 the same as the P. spinosus of Bohemia. 



Mr. Ordway replied that from the examination of a considera- 

 ble number of specimens, he was satisfied that they are distinct 

 species, and he would soon make to the Society a communication 

 giving his reasons for this opinion. 



Prof. Rogers stated that Barrande's means of solving this ques- 

 tion were scanty, consisting of a few casts in Paris and some pho- 

 tographs sent by himself. Barrande thinks them the same ; but 

 if this opinion should be reversed on full examination, and the two 

 be ascertained to be distinct species, or still better, strongly marked 

 varieties, it would coincide well with his present views on the 

 origin and modification of species. 



