530 Dr. A. Vauyhan — The Lower Culm of North Devon. 



EXPLANATION OF PLATE XVII. 



Shell of the type-specimen of Tcsticdo Amnion, photographed from the side. Reduced 

 to about ^ natural size. From the L^pper Eocene beds of the Fayum, Egypt. 



Eeproduced from a photograph made in the G-eological Museum, Cairo : copied with 

 the pennission of Captain 11. G. Lyons, F.G.S., the Director- General ot 

 the Geological Survey of Egypt. The original specimen was obtained 

 by H. J. L. Beadnell, Esq., F.G.S. , of the Geological Svu-vey, during his 

 excavations in the Fayum early in 1902. 



II. — Note on the Lower Culm of North Devon. 



By Arthur Vaughax, B.A., D.Sc, F.G.S. 



IN the Geological Magazine, August, 1904, pp. 392-403, 

 L Dr. Wheeltou Hind describes the Lower Culm beds of North 

 Devon and assigns them to the ' Pendleside ' series. 



From the original paper ^ dealing with that series I gather that in 

 the North of England the 'Pendleside' beds lie above the uppermost 

 zone of the Carboniferous Limestone, and are the equivalents of 

 the Millstone Grit of the South Wales and Mendip areas. Dr. Hind's 

 contention is, then, that the Lower Culm of North Devon was laid 

 down at a time subsequent to tlie deposition of the whole of the 

 Carboniferous Limestone of the Mendips and South Wales. 



The Carboniferous Limestone of South Wales, Chepstow, Bristol, 

 and the Mendips lies but a short distance N.E., N., and N.W. of the 

 Culm crop. It seems then highly probable that, if any difference 

 exists, the faunal sequence in North Devon will resemble that of the 

 neighbouring areas, rather than that of Lancashire and the Midlands. 



It is, without doubt, an astonishing instance of the geographical 

 inversion of the faunal sequence that Brachiopods and Corals which, 

 in the North, occur in supra- Visean beds should, in the South, be 

 only characteristic of infra-Visean rocks. 



Eemarkable as this phenomenon unquestionably is, it scarcely 

 affects the purpose of this note, which is to demonstrate that, if the 

 fanned sequence in North Devon is identical with that in the neighbouring 

 areas, the Lower Culm must be placed, not above the Visean, but 

 well below the uppermost limit of the Tournaisian or lower division 

 of the Carboniferous Limestone. 



If the Carboniferous Limestone be studied in the extreme west 

 at Tenby, in the neighbourhood of Severn Tunnel Junction, or in 

 the Forest of Dean, in the Sodbury and Bristol areas, or at its most 

 southerly crop in the Mendips, the faunal sequence is essentially 

 the same at all points; furthermore, this result is deduced from 

 continuous sections in which there is no possibility of misreading 

 the order of the beds. Throughout the Carboniferous Limestone 

 outcrop which lies nearest to the Culm of North Devon the faunal 

 facies varies from zone to zone, but the same fossil assemblage 

 always characterizes the same horizon, even if the points at which 



' "The Pendleside Group at Pendle Hill, etc.," by Dr. 'NVheelton Hind and 

 Mr. J. A. Howe: Q.J.G.S., vol. Ivii (1901), p. 388. 



