SPIRIFERA. 43 



to be lower beds at Petherwin, in Cornwall. Herr A. Roemer has also found larger 

 examples of this shell in the Devonian beds of Grand, in the Hartz. 



? Spirifera lineata, Martin (sp.). PI. IV, figs. 13 — 15, 10. 



Conchiliolithus Axomites lineatus, Martin. Petref. Derb., pi. xxxvi, fig. 3, 1809. 



Terebratula lineata et tmbbicata, Sowerby. Spirifer Martini, Fleming. 



Spirifera lineata, Phillips. Pal. Toss, of Cornwall, Devon, and West Somer et, p. 70. 



pi. xxviii, fig. 120, 1841. 

 ? — microgemma, Phillips. Ibid., p. 68, pi. xxvii, fig. 11G. 



there are also some species common to Devonian beds and the Silurian system ; whilst by far the greater 

 number are neither Silurian nor Carboniferous, but intermediate forms, that is, they represent an inter- 

 mediate period, if it be possible for fossils to do so. The results of Mr. Jukes' examination of these Irish 

 beds, and of their fossils, will be found in the ' Explanations of the Geological Survey of Ireland ;' and 

 at pp. 215, &c. (also foot-note, p. 185) of the same author's ' School Manual of Geology.' This subject 

 will, however, require much further examination, and it will be necessary for all the classes of fossils 

 found in the North Devon and South of Ireland brown grits and slates to be carefully compared with 

 Carboniferous types, before any positive determination relative to the age of these beds be finally settled. 

 In Ireland we appear to have, first, some Upper Silurian rocks, full of marine mollusca, Brachiopodu, 

 &c. ; then, a very thick formation, of what Mr. Jukes terms Dingle beds, resting conformably on the upper 

 Silurian, but covered unconformably by genuine Old Red Sandstone, neither containing any Brachiopoda ; 

 above this, a very thick succession of slaty and sandy beds or grits, full of marine fossils, and containing 

 a mixture of Devonian and Carboniferous species of Brachiopda ; and above part of this, again, beds of 

 Carboniferous himestone, full of genuine Carboniferous fossils and Brachiopoda ; while other parts have 

 no limestone over them, but in some places shales, that appear to be Coal-measures, the parts not covered 

 by the limestone being much thicker than those that are. 



Mr. Jukes informs me that he has now arrived at the following general conclusions : 



1st. That the uppermost bed of the true Old Bed Sandstone was in existence before any of the beds 



containing marine Devonian fossils were deposited. 

 2nd. That the Devonian fauna was contemporaneous with the Carboniferous, the terms really 

 indicating a geographical and not a chronological distinction. He believes this will ultimately 

 be found to be true for America as well as Europe. 

 3rd. That the so-called Old Red Sandstone of Wales and Scotland belongs to two periods, distinct 

 in their forms of life, the one (containing Cephalaspis, &c.) belonging more properly to the 

 Upper Silurian, the other being more closely connected with the Carboniferous. 

 4th. He would limit the term Old Red Sandstone to the latter; and his first conclusion will then 

 show the confusion produced by using the words " Old Red Sandstone" and "Devonian" as 

 synonymous. 

 In his valuable paper "On the Upper Old Red Sandstone and Upper Devonian Rocks " (' Journal of 

 the Geol. Soc. of London,' vol. xix, p. 490, &c, 1863), Mr. Salter, with the concurrence of Sir R. 

 Murchison, refers the Marwood and Pilton beds of North Devon to the Upper Devonian (Verneuilii- 

 Schiefer, &c). The Petherwin and Landlake group he considers to constitute a lower band also of the 

 Upper Devonian, but not to represent that of Barnstaple or of the Marwood and Pilton series, these last 

 being the equivalents of the Clymenien-Kalk or Cypridinen-Schiefer of the Prussian geologists, and, perhaps, 

 of the red slates of Morte Bay ; so that, in Mr. Salter's opinion, the Marwood and Pilton Beds overlie the 

 Petherwin group. 



