Vol.51.] RADIO LARIAN ROCKS IN THE LOWER CUL1I MEASURES. 6 L7 



as the Codden Hill Quarry (fig. 1). The face of this quarry is about 

 60 feet in height. The beds are mainly of hard, dark or light grey, 

 sometimes banded, cherty, siliceous rock, with intermediate beds 

 of soft grey or white siliceous shale, which run with an even 

 thickness and in regular succession from the summit to the bottom 

 of the quarry. The dip is 60° N". In the soft shaly beds here the 

 radiolaria can be distinctly seen with a lens, but they are ouly 

 visible in certain portions of the hard cherty beds. 



Overton Quarry, on the southern side of Codden Hill, is almost 

 entirely of white and grey beds, which dip N".E. at 55°, while in 

 the Tower Hamlet Quarry, at the eastern end of the hill, dark 

 and light grey siliceous beds are intermingled. 



East of Codden Hill is another elongate ridge, known as Hang- 

 man's Hill ; at one end of this is Bableigh Quarry, in which the beds 

 dip 60° S.S.W. At the opposite or eastern end of this ridge, on the 

 •road leading to Hannaford, is a quarry about 50 feet in height, in 

 which the beds are alternately of dark, hard, compact, siliceous rock 

 and of soft, white, siliceous shales. There are also one or two thin 

 beds of a yellowish or bun , light, porous, siliceous shale or rotten- 

 stone containing casts of trilobites and brachiopods as well as empty 

 casts of radiolaria. These latter, associated with hexactinellid 

 spouge-spicules, are also very abundant in the soft white shales, but 

 less recognizable in the harder compact beds. The strata in this 

 quarry are nearly vertical, with an east-and-west strike. 



Continuing farther eastward, at Swimbridge, about 5 miles 

 S.E. of Barnstaple, a considerable thickness of siliceous rocks is 

 exposed in a large quarry immediately north of the village. The 

 beds are nearly vertical ; they consist mainly of dark, hard, platy, 

 compact rock, but occasionally lighter bands occur in which the 

 radiolaria can be seen with a lens. 



Beyond Swimbridge, following the high road for a distance of 

 about 2 miles to the S.E., at the summit of Heddon High Down 

 there are extensive quarries. At the most westerly of these, the 

 beds are almost entirely made up of hard, dull black, siliceous rock 

 with wavellite developed on the joint-planes. They dip 65° N. 

 Some of these black beds are crowded with radiolaria, which are 

 visible, however, only in thin microscopic sections. In the quarries 

 at the eastern end the beds are nearly vertical ; the lower ones aie of 

 black rock similar to that just mentioned, but above these there is 

 a series of hard, light-grey, or whitish beds, without any admixture 

 of the dark rock. Radiolaria are very abundant in the lighter beds, 

 and they can be readily seen with a lens. 



Returning now to the neighbourhood of Barnstaple, on the west 

 side of the Taw River, nearly in a line with Codden Hill, is another 

 ridge, extending for a little more than a mile in a westerly direction 

 as far as Templeton, about 3 miles S.W. of Barnstaple. On this 

 ridge quarries have been opened at Tawstock, Corffe Lodge, and at 

 Templeton. We have not visited these quarries, but from informa- 

 tion supplied to us by Mr. J. G. Hamling and from specimens of the 

 beds we have ascertained that the rocks are precisely similar in 



