1. Rogers 8^ E. A. Newell Arber — Culm of West Devon. 305 



IV. — Note on a new Fossiliferous Limestone in the Upper 

 Culm Measures of West Devon. 



By Inkermann Rogers, and E. A. Newell Arber, M.A., F.L.S., F.G.S. 



AT the present time we are only fully acquainted with the 

 geology and palaeontology of one division of the great 

 Carboniferous Series developed in Devon and the adjacent counties, 

 the Lower Culm Measures. This division, while representing only 

 a small fraction of thickness of the Culm Measures as a whole, 

 is of special interest both lithologically and palaeontologically, as 

 was shown by Messrs. Hinde & Fox ^ in an admirable paper 

 published in 1895. x\bove the limestones and cherts of the Lower 

 Culm Measures lie the great thickness of sandstones and shales 

 which constitute the Upper of the twofold primary division of these 

 rocks instituted by Sedgwick & Murchison - in 1840. The Upper 

 Culm Measures occupy an area of more than 1,000 square miles, 

 and are of Upper Carboniferous age. 



With the exception of the researches of the late Townshend Hall, 

 and more recently of Mr. Ussher, comparatively little has been 

 added to our knowledge of these beds since the days of Sedgwick & 

 Murchison, and of De la Beche. An inquiry with regard to the 

 palseontology, and more especially the pala^obotany, of these rocks 

 has, however, been in progress for some time past, with the result 

 that sufficient material has been gathered for a contribution to the 

 fossil flora of the Upper Carboniferous rocks of Devon, which it 

 is hoped will be published shortly by one of us. While examining 

 the sandstones and shales of this series, other discoveries have been 

 made, incidental to the work of collection of plant-remains. Among 

 these the discovery of fossiliferous calcareous nodules, and, in one 

 locality, of a limestone band, seems to warrant special notice. 



So far no limestones have been known to occur in the Upper 

 Culm Measures. Even in the Lower Carboniferous portion of the 

 Culm Measures the general absence of calcareous deposits is somewhat 

 sharply contrasted with the Lower Carboniferous sequence developed 

 elsewhere in Britain. Limestones do, however, occur in this series. 

 They form inconstant and impersistent bands, seen at Swimbridge 

 and Venn near Barnstaple, and in other localities, and are generally 

 believed to underlie the Coddon Hill beds, though Mr. Ussher^ 

 is inclined to regard them as superior to the cherts. On the other 

 hand, the only calcareous sediments known from the Upper Culm 

 Measures are the calcareous shales and shaly nodules containing fish 

 and Goniatite remains occurring at Instow, near the junction of 

 the Taw and Torridge, which were described in 1876 by the late 

 Townshend Hall * in the Geological Magazine. 



The Instow beds lie, so far as we have been able to ascertain, 

 near the base of the Upper Culm Measures, and, although the 



1 Hinde & Fox: Quart. Journ. Geol. Soc, vol. 11 (1895), p. 609. 



2 Sedgwick & Murchison: Trans. Geol. Soc, ser. ii, vol. v (1840), p. 633. 



2 Ussher :. Proc. Somerset Arch, and Nat. Hist. Soc, vol. xxxviii (1892), p. 121. 

 4 Hall: Geol. Mag., Dec II, Vol. HI (1876), p. 410. 



decade v. — vol. I. — so. Til. 20 



