Vol. 51.] RADIOLARIAN ROCKS IN LOWER CULM MEASURES. 609 



43. On a Well-markeb- Horizon of Radiolarian Rocks in the 

 Lower Culm Measures of Devon, Cornwall, and West 

 Somerset. By George Jennings Hinde, Ph.D., F.G.S., and 

 Howard Fox, Esq., F.G.S. (Read June 5th, 1895.) 



[Plates XXIII. -XXVIII.] 



Contents. 



Page 

 I. Introduction 609 



II. Literature relating to the Radiolarian (Oodden Hill) Beds . 611 



III. Distribution of the Radiolarian Beds 615 



(a) Barnstaple District, N. Devon. 



(b) Dulverton, W. Somerset. 



(c) Ashbrittle, W. Somerset. 



(d) Holcombe Rogus, Canonsleigh, and Westleigh, N.E. 



Devon. 



(e) Boscastle District, Cornwall. 

 (/') Launceston District, Cornwall. 

 (ff) Tavistock District, Devon. 



(h) Ramshorn Down, near Bovey Tracey, S.E. Devon. 



(i) Chudleigh District, Devon. 



(k) Bishopsteignton, near Teignmouth, S.E. Devon. 



IV. Mode of Occurrence of the Radiolarian Rocks 627 



V. Chemical Composition of the Radiolarian Rocks 629 



VI. Microscopic Characters of the Radiolarian Rocks 629 



VII. Description of the Radiolaria 633 



VIII. Description of the other Fossils associated in the same Rocks 



with the Radiolaria 643 



(a) Sponges. 



(b) Corals. 

 (<;) Crinoids. 



{d) Trilobites. By Dr. Henry Woodward, F.R.S., P.G.S. 



(c) Brachiopoda. By F. A. Bather, Esq., M.A., F.G.S. 

 (/) Cephalopoda. By G. C. Crick, Esq., F.G.S. 



Tables of Fossils (I. & II.). 

 IX. Position of the Radiolarian (Codden Hill) Beds in the Lower 



Culm Series 656 



X. Correlation of the Radiolarian Beds 658 



XI. Summary and Conclusions 660 



I. Introduction. 



The general character and succession of the Culm Measures or 

 Carboniferous series of Devon and adjacent portions of Cornwall 

 and West Somerset, worked out by Sedgwick and Murchison, De la 

 Beche, and John Phillips in the years 1836-1842, have in the 

 main been regarded by geologists as correct ; and the alterations 

 and additions to their descriptions which have been made by the 

 subsequent researches of the late Dr. Holl, Mr. T. M. Hall, and of 



