1851.] SEDGWICK SLATE ROCKS OF DEVON AND CORNWALL. 7 



be to invert the whole logic of geology, and could produce nothing 

 but confusion and incongruity of language. 



Soon after the publication of the paper on the Devonian System 

 by Sir R. I. Murchison and myself, Mr. Griffith re-examined some 

 large deposits in the South of Ireland, finally separated them from 

 the older rocks, and, on the evidence of their fossils, determined by 

 Professor M'Coy, arranged them with the Carboniferous System, 

 giving them the name of Carboniferous Slates. At the same time 

 he stated that many of the fossils in the " carboniferous slates " were 

 identical with the species found in the highest Devonian Groups — 

 those of Petherwin and Barnstaple. Since that time doubts have been 

 entertained respecting the line of demarcation between the Devonian 

 and Carboniferous systems ; nor have these doubts been invalidated, 

 but rather confirmed, by the excellent and copious lists of fossils pub- 

 lished and described by Prof. Philhps. I rejoiced, therefore, in having, 

 during the past summer, the assistance of Prof. M^Coy in examining 

 the quarries near Petherwin and the sections immediately north of 

 Barnstaple ; and I will endeavour to give some of the results of this 

 examination in a very condensed form. 



Petherwin Quarries. — Here were found two species of Trilobites 

 of the genus Portlockia, viz. P. latifrons, Bronn, and P. granu- 

 lata, Miinster. The same genus occurs at Croyde Bay, N.W. of 

 Barnstaple, and it is found in the Eifel country. Taken by itself, it 

 would be considered Devonian ; for the Carboniferous genera have 

 hitherto been confined to Phillipsia and Griffithides, M*Coy. The 

 genus Clymenia, which I first saw in 1836, is very abundant near 

 Petherwin, especially in the old Lanlake quarry. Phillips gives seven 

 species from this locality*. Through the kindness of Mr. Pattison 

 we are enabled to add to this list one of Miinster' s species (C bisul- 

 catd)^ and three others that are new, viz. Clymenia Pattisoni, C. qua- 

 drifera, and C. Miinsteriy M'Coyf. We found also Producta sub- 

 aculeata, Murch., a true carboniferous-slate fossil. Near this quarry 

 I also found in 1 836, close to the overlying black culm-slates, innu- 

 merable examples of a small Bivalve, the Sanguinolaria elliptica, 

 Phillips. This species is also found in very deep denudations near 

 Yeolm Bridge, and at Underwood Farm, several miles wdthin the 

 south boundary of the culm-measures. In these places, which have 

 been described by Mr. Pattison J, all the overlying culm-shales have 

 been swept away ; and the Petherwin Group, abounding in fossils, 

 has been brought to the denuded surface in the form of a saddle. 

 For many other species of the Petherwin fossils I must refer to the 

 copious list given by Phillips §. 



Baggy Pointy Marwood, Barnstaple, ^c. — At Baggy Point we 



* See Palaeozoic Fossils of Devon, Cornwall, and W. Somerset, 1841, p. 124. 



t See " Description of the Palaeozoic Fossils in the Cambridge Museum," 4to, by 

 Prof. M'Coy, forming Part II. of the " Synopsis of the Classification of the British 

 Palaeozoic llocks, by Prof. Sedgwick." The first " Fasciculus " of Part II. has ap- 

 peared, the second is in the press. 



X See Trans. R. Geol. Soc. Cornwall, vol. vii. p. 64. 



§ Op. cit. Synopsis, p. 142 et seq. 



