Some Pakeohotanical As'peds. 277 



ogy if the Eiversdale plants, whose correlation by Sir 

 William Dawson with the Millstone Grit is not likely to 

 prove far from correct, were now to be pronounced Devon- 

 ian on account of their paheontological identity with the 

 fern ledges whose erroneous reference to the Devonian was 

 earlier forced upon Sir William by the findings of the 

 stratigraphers. The study of the plants collected at sev- 

 eral hundred localities in the Pottsville formation along 

 the Appalachian trough proves conclusively that the St. 

 John flora is from nearly the same stage, while, as I have 

 elsewhere pointed out,^ it is probable that a portion of the 

 section at the " fern ledges " ^ is contemporaneous with 

 the upper portion of the Pottsville. 



The MacKay's Head Plant Beds. 



MacKay's Head, another of the sections now placed in 

 the Hamilton, furnished a number of the species described 

 in 1873 by Sir William Dawson and referred by him to 

 the Millstone Grit. Dawson's list includes alternate- 

 ribbed species of Calamites, a large Carboniferous type of 

 Zepidodendro7i identified by him as L. aculeatum, a fern 

 figured as " Odo7itopteris ? " , aud other ferns identified as 

 Alethopteris lonchitica and Sphenopterts ohtusiloba. These 

 species, though few in number, are recognized by palteo- 

 botanists as distinctly Carboniferous. The material is 

 hardly sufficient for a definite correlation, but it seems 

 probable that the flora, especially the Lep)idodendron and 

 the Ahtlwptcris, will eventually be found to lie above the 

 Carboniferous Limestone. The small amount of published 

 plant evidence points towards the Pottsville or Millstone 

 Grit, to which the MacKay's Head beds were referred by 

 Sir William Dawson. 



1 20th Ana. Rept. U.S. Geol. Surv., pt. 2, 1900, pp. 913, 917. 



2 Dr. G. F. Matthew suggests the refevence of a portion of the St. Jolni fern ledges 

 to the Silurian. 



