'328 Rocks and Fossils of PhiUipshurgh, C. jh. 



which towards the base contains layers of reddish limestone inter- 

 stratified with red sandstone, — marking the transition from the are- 

 naceous to the calcareous form of deposit. 



" In none of the localities of this calcareous mass which I have 

 examined, from the flank of the Snake Mountain to near the Ca- 

 nada line, have I found any well-marked organic remains. This 

 fact of itself strongly favors the idea of its being but a peculiar de- 

 velopment of the upper portion of the Medina group. Nor can it 

 be objected to this that metamorphic action may have caused its 

 present destitution of fossils. Through nearly the whole of the 

 series of exposures extending due north toward the Canada line, it 

 presents a gentle eastern dip, conforming to the subjacent fossili. 

 ferous beds of Matinal limestone and slate, from which it is sepa- 

 rated only by the sandstones above described. From this we infer 

 that it must have been as little exposed as these fossiliferous beds 

 to agencies capable of obliterating its included fossils, and that 

 therefore it has never been in any considerable degree a fossiliferous 

 mass. 



" We are further strengthened in the opinion that this calcareous 

 group, with the subjacent sandstone, belongs to the Medina period 

 by the consideration that the Clinton group, with which it might 

 otherwise be compared, is almost everywhere an eminently fossili- 

 ferous one. From Alabama to northern New York, it is marked 

 by an abundance of fossils. According to Mr. Logan, strata of 

 this age are found in the vicinity of Lake Memphremagog, and, 

 although there surrounded by metamorphic masses, they include a 

 number of fossils in good preservation. 



" On the whole, therefore, I think that the limestone and sub- 

 jacent sandstone of which we are now treating must be regarded 

 as one formation, and may with the highest probability be referred 

 to the period of the Levant rocks or the Medina group of New 

 York." 



A careful re-examination of Snake Mountain is much required, 

 for if the section it presents has been correctly interpreted then 

 we must admit that palaeontology is at fault, but if the displace- 

 ment contended for by Emmons really does exist then the princi- 

 ples of the science will remain as before, unerring guides for us in 

 our researches after truth. 



