Table IV. — The Radiolarian Phase at the Base of P. 



CI) 



Fauna!. 1 



o O 





(2) Stratigraphical 

 and 

 Lithological. 



Characters distinguishing the phase 



from ordinary shallow-water 

 marine formations. 



Ordinaiy sediments 

 within the phase. 



included 



Relations to the beds : — (1) below 



The sole macroscopic organisms of some interbedded shales 

 are the lamellibranchs (unbroken) mentioned on p. 551, 

 known elsewhere only from shallow-water formations 

 (Gower). 



Occurrence as a thin group coni'ormablj- intercalated 

 between two shallow-water formations, — the Rotten- 

 stone Beds and the Millstone Grit (Carmarthenshire 4 ) 



Presence of intercalated beds of ' culm ' (coal), several 

 inches thick (Barnstaple 2 ). 



Lenticular, wedge-bedding of many lamina?, the latter 

 sharply defined and differing considerably in composi- 

 tion one from the other. 



Fine grain of the terrigenous material. 

 Abundance of radiolaria. 



Very rare, if existent : for, although some beds resemble 

 ordinary shales and silts and, in Devon, some contain 

 corals, etc., 3 radiolaria appear to be abundant through- 

 out and no coarse sediment is known. 



(2) above 



Conformably resting upon the Rottenstone Beds in Car- 

 marthenshire. 4 



Not known with certainty in Gower, Pembrokeshire, oi 

 North-Western Devon. 5 



Sharp, but conformable, change to the Millstone Grit in 



Carmarthenshire. 4 

 Not known with certainty in Gower, where the group 



gives place to shales, apparently without recurrences of 



radiolarian cherts. 

 Not known with certainty in North-Western Devon. 



Development in (1) Bristol area 



(2) Gower 



(3) outcrops south 

 of the Pem- 

 brokeshire 

 coalfield. 



(4) North -West 

 ern Devon. 



Absent. 



Present throughout (and to the north in Carmarthenshire). 

 Present throughout, except in the southernmost (Boshes 

 ton) outcrop. 



Present throughout 6 ; thickness, and probably duration 

 also, much greater than in South Wales. 



Note. — Features of general occurrence are not followed bj^ the name of a locality. 



1 The fauna of the Devon development, as recorded by various authors, contains no forms 

 which need be supposed to have lived at great depths. For lists see G. J. Hinde & H. Fox, 

 op.cit., — all orders; H.Woodward, Geol. Mag. 1902, p. 481, — trilobites; Wheelton Hind, Geol. 

 Mag. 1904, p. 398, — all orders ; A. Vaughan, Geol. Mag. 1904, p. 531,— brachiopods and corals.. 



- First brought to mv notice by Mr. J. G. Handing. 



3 G. J. Hinde & H. Fox, Q. J. G. S. vol. li (1895) pp. 617, 643 etseqq. 



4 T. C. Cantrill in ' The Country around Ammanford ' Mem. Geol. Surv. 1907, p. 75 ; and 

 in conversation. 



5 The Devonian and Lower Culm of Fremington Pill, Barnstaple, said by De la Beche to 

 pass one into the other ('Rep Geol. Cornwall, Devon, & West Somerset' Mem. Geol. 

 Surv. 1839, p. 103), appear at present to be confined to isolated exposures affording no 

 evidence on the question. 



6 G. J. Hinde & H. Fox, op. snjjra cit. 



Q. J. G. S. No. 268. ' 2 o 



