318 Geological Society : — 



authors do not include in this series all the beds which have been 

 referred to it by others. The term ' Grits,' which has been used in 

 connexion with these beds, is a misnomer; there are beds which 

 are superficially like fine grits, but they are found to be radiolarian 

 deposits. 



The Codden Hill Beds occur along a comparatively narrow belt 

 of country, a short distance within the northern and southern 

 boundaries between the Carboniferous and Devonian systems. 

 Starting with the northern exposures, the authors give a descrip- 

 tion of the beds as developed in various localities from the neigh- 

 bourhood of Barnstaple (Codden Hill itself, situated 3 miles S.E. 

 of Barnstaple, being a convenient starting-point), past Dulverton, 

 to Ashbrittle in West Somerset. On the south the beds are 

 traceable from Boscastle to the neighbourhood of Tavistock, and on 

 the east side of the Dartmoor granite they are found near Chudleigh 

 and Bovey Tracey. 



At present there are not sufficient data for estimating the 

 thickness of the radiolarian deposits ; but they are probably 

 some hundreds of feet thick, though the whole does not consist 

 of beds of organic origin. In a quarry in the Launceston district 

 50 feet of radiolarian cherty rock are seen without admixture of 

 shale. 



A detailed description of the lithological characters of the rocks 

 of the series is given, and analyses by Mr. J. Hort Player ; a 

 marked feature of their composition is the very general absence of 

 carbonate of lime. The microscopic characters of the rocks are also 

 described, and the small amount of detrital matter in the beds of the 

 series is noted. 



Forms belonging to 23 genera of radiolaria have been recog- 

 nized, included in the orders Btloidea, Sjphceroidea, Prunoidea, 

 Discoidea, aud Cyrtoidea; in addition a scanty but significant fauna 

 of corals, trilobites, brachiopods, and cephalopods is present in 

 some thin shaly beds near Barnstaple. Nearly all the forms arc 

 diminutive. The trilobites are described by Dr. H. Woodward, the 

 brachiopods by Mr. F. A. Bather, and the cephalopods by Mr. G. C. 

 Crick. Of the 25 species of fossils other than radiolaria which 

 have been determined, several are only known elsewhere from the 

 Lower Culm of Germany, while others are common to the Carboni- 

 ferous Limestone of the British Isles and Belgium. 



These fossils tend to confirm the view that the Lower Culm 

 Measures are the deep-water equivalents of the Carboniferous 

 Limestone in other parts of the British Isles, and not shallow-water 

 representatives of deeper beds occurring to the north, as was formerly 

 supposed. In connexion with this it is worthy of note that the deep- 

 sea character of the Lower Culm of Germany, which corresponds 

 with our Lower Culm Measures, Avas maintained by Dr. Holzapfel 

 even before the discovery of radiolaria in the beds of Kieselschiefer 

 furnished such strong evidence in support of this view. 



