334 



THE GEOLOGIST. 



the chronological equivalents of the " Old Red" of Herefordshire and 

 Scotland — much as they differ lithologically and palseontologically. 

 Scotland does not yield the shells, corals and sponges so abundant in 

 Devonshire ; nor are the ichthyolites, with which the Scotch rocks 

 teem, found in the latter district : this, however, has ceased to be a 

 chronological difficulty, since the author of " Siluria" found the fossils 

 characteristic of each of the areas lying together in the same Devonian 

 beds in Russia.* 



It is but right to add that many geologists well acquainted with 

 the Devonshire rocks have accepted this chronological decision in a 

 more or less modified form. Thus, the late Sip H. de la Beche 

 regarded " The bulk of the Devonian and Cornish rocks as at least 

 in part equivalent to the lower beds of the Carboniferous limestone, 

 to the passage-beds between the Old Red Sandstone and Carboni- 

 ferous limestone of Ireland, South Wales, &c, and also to some 

 portion of the higher part of the Old Red Sandstones of Hereford- 

 shire and adjacent districts.' ; f The late Rev. David Williams 

 considered the Devonian system as occupying "an enormous interval 

 between the Old Red Sandstone and the Mountain-limestone. "J 



The late Mr. D. Sharpe, Professor Jukes, and Mr. Austen, have 

 advocated the view that the rocks of Barnstaple in North Devon, 

 and South Petherwin in Cornwall, belong to the Carboniferous 

 system ; whilst Mr. Salter would modify this, and class the upper 

 portion of the Barnstaple group only as Carboniferous. The chro- 

 nology of the Barnstaple and Petherwin beds will again come under 

 notice, when discussing the distribution of the fossils of Devon and 

 Cornwall. 



That life existed on the earth during the era of the Devonian 

 rocks is evidenced by the fossils they contain ; unless, with the 

 author of " Omphalos," we hold them to be jprochronic. Indeed, 

 the introduction of life dates very much earlier than this, since no 

 fewer than very nearly one thousand species of organisms are 

 recorded as having become extinct in Britain alone, in pre-Devonian 

 times. The following table exhibits the amount and variety of life 

 in the period under consideration, as compared with the fauna and 

 flora now existing. "** 



The figures in the 1st, 2nd, and 6th columns are copied from 

 Bronn's " Index Paleeontologicus," Quart. Journ., Geol. Soc, vol. i., 

 page 44 ; and those in the 3rd, 4th, 7th, and 8th, are compiled 

 from Professor Morris's Catalogue of British Fossils. It has been 

 thought best to take no liberties with the originals, so that the 

 authors alone are responsible for the correctness of the figures, which 

 though possibly incorrect in a few cases, are on the whole the best 

 that can be commanded. 



* " Siluria," 3rd Edition, page 382. 

 f Mem. Geol. Survey, vol. i., p. 103. 

 X Report Eoyal Geol. Soc. of Cornwall (1813), p. 123. 



