114 Mr. Weaver oji the Older Stratified 



juxta-position of formations, all will admit that we cannot 

 draw a direct inference as to their relative age. 



Thirdly, as to the relative age of the Older Stratified Rocks 

 of North Devon, extending from theTrilobite slates near Barn- 

 staple on the S. to the Foreland sandstone on the N. In 

 now considering these deposits as the equivalents of the Old 

 Red Sandstone, the authors appear to have been led partly by 

 relying on an apparent conformity and gradation between the 

 Trilobite slates and the superincumbent carboniferous rocks, 

 and partly and chiefly from observing that in these Older 

 Stratified Rocks, though distinguished by many transition 

 fossils, are yet to be found certain Spiriferae, Products?, and 

 Terebratulae, with perhaps some other organic exuviae, similar 

 to such as occur in the carboniferous series ; at the same time 

 throwing overboard all regard for the mineralogical distinc- 

 tions which are observable in these Older Stratified Rocks*. 

 With respect to the two first points, the supposed conformity 

 and gradation, I have already expressed the grounds of my 

 dissent ; and with regard to the third, the occurrence of cer- 

 tain Spiriferae, Products, and Terebratulae, it may be re- 

 marked, that so far back as the year ]824't I intimated that 

 some species of those genera are common both to the transi- 

 tion and carboniferous epochs; and in my observations on 

 the South of Ireland between that year and 1830, and re- 

 newed in the year 1834, I was confirmed in that view, and 

 which has been since set forth in my Memoir on that portion 

 of the island (published in 1837), in which I have shown that 

 in particular several species of those genera, besides others, 

 occur in various countries both in the transition and carboni- 

 ferous systems |. From analogous occurrences in the lime- 

 stones of South Devon, at Plymouth, &c., Professor Phillips 

 was induced in 1833 to express doubts as to whether those 



* Governed by these views, the authors propose the term Devonian 

 System, to comprise " all the great intermediate deposits between the Si- 

 lurian and Carboniferous systems." (Lond.and Edin. Phil. Mag., vol. xiv. 

 p. 259. April 1839.) But, it may be asked, what evidence have we of 

 this intermediate position ? Where do we find those deposits resting on the 

 Silurian system, and passing upward into the old red sandstone? 



t Geol. Trans., vol. i. second series. Observations in Gloucestershire 

 and Somersetshire, §. 9. p. 329. 



X Geol. Trans., vol. v. second series. Memoir on the South of Ireland. 

 § §. 13, 33, 57. — N.B. In that memoir I did not em])loy Dalnian's genus of 

 Atrypa, as including certain Spiriferae and Terebratu la?. Von Buch having 

 shown that Dalman's distinction was founded in a mistake. (See Uebcr die 

 Terebrnteln von Leopold von Buch, p. 23. Berlin, 1834.) Mr. J, de C. 

 Sowerby, however, adopted that genus. (See Min. Conchol., Aug. 1835. 

 See also 8ilurian System, pp. 643,644.) 



