614 DR. G. J. HINDE AND MR. HOWARD FOX ON [Nov. 1 895, 



near Launceston, and at Codden Hill near Barnstaple, where they 

 contain Goniatites and crinoidal stems. 



Messrs. Chanrpernowne and Ussher, 1 in ' Notes on the Structure of 

 the Palaeozoic Districts of West Somerset' (1879), describe the Codden 

 Hill Beds exposed at Hulverton Hill, near Dulverton Station, as 

 ' easily distinguishable by their baked appearance, whitish buff or 

 dark-grey colour, and frequent chertoid texture ; they consist of 

 thick shales or thin fine-grained grits in tabular layers, so inter- 

 sected by even joints as to afford a valuable road-metal without 

 further fraction.' 



Mr. H. B. Woodward, in the 2nd edition of the ' Geology of 

 England and Wales ' (1887), 2 places at the base of tbe Culm Measure 

 series the shales, thin grits, and impersistent beds of limestone 

 with occasional beds of Culm (Posidonomya-\im.estone) as probably 

 representing the Lower Carboniferous ; next above are the Codden 

 Hill Beds (local), probably on the horizon of the Millstone Grit ; 

 and succeeding these are the sandstones, grits, and shales, with 

 beds of Culm, which may be of the age of the Lower Coal Measures. 

 The Codden Hill Beds are described as consisting of pale grey or 

 black chert in thin striped beds, with black grits, jasper rock and 

 lydian-stone and a variable thickness of shales, the total thickness 

 of which had been estimated by the Rev. 1). Williams at from 

 1500 to 2000 feet. 



Lastly, these rocks have been very comprehensively described by 

 Mr. W. A. E. Ussher in the ' British Culm Measures,' 3 which con- 

 tains, moreover, a summary and revision of his own previous works 4 

 on the subject. He divides the Culm Measures from below 

 upwards into Basement Beds, Exeter type, Lgbrooke Park Beds, 

 Morchard type, and Eggisford Grits. It is only with the lower 

 division, or the Basement Beds, that we are concerned in this paper. 

 These consist of the dark limestones and shales and the Chert or 

 Codden Hill Beds. The author considers that Phillips may possibly 

 be right in placing these latter above the shales and limestones of 

 Venn and Swimbridge, and he also assigns the same relative position 

 to the outcrops at Ashbrittle, West Somerset. The typical beds at 

 Codden Hill itself are described as thick, buff, whitish, and dark- 

 grey shales, fine shaly grits and cherty mudstones, and they are 

 stated to be represented in South Devon by hard, thin, evenly-bedded 

 fine grit with an abundance of Goniatites spiralis, and, further, it 

 is suggested that the hard beds with Posidonomya Becheri and the 

 soft and hard beds at Waddon Barton may belong to the same type. 

 No mention whatever is made of a possibly organic origin of the 

 cherty beds, which are, however, recognized as identical in character 

 with the kieselschiefer of the German and the phthanites of the 

 Erench and Belgian geologists. 



1 Quart. Journ. Geol. Soc. vol. xxxv. (1879) p. 532. 2 P. 197. 



3 Proc. Somerset. Archseol. & Nat. Hist. Soc. vol. xxxviii. (1892) pp. 111-219. 



4 Eep. Brit. Assoc. (1881) pp. 629-631 ; ibid. (1886) p. 676 ; Proc. Som. 

 Arctueol. & Nat. Hist. Soc. vol. xxv. (1879) pt. ii. pp. 1-20, vol. xxxvi. (1890) 

 pp. 97-104 ; Geol. Mag. 1887, pp. 10-17; CongresGeol. Int. 4 me sess. Londres, 

 1888, p. B 141. 



