Vol. 51.] RADIOLARIAN ROCKS IN THE LOWER CULM MEASURES. 621 



Cliff, the cliffs show an apparently continuous succession of shales 

 or slates and grits, marvellously folded and twisted and interpene- 

 trated in all directions by quartz-veins, but without, so far as we 

 could observe, any further developments of cherty rock. The dip 

 of the beds throughout this distance is steadily northward, at an 

 average angle of 25°. No mention of this cherty rock near Boscastle 

 is made by De la Beche, although it for ms a very prominent feature, 

 and is markedly distinct from the shales above and below. It may 

 also be mentioned that in this district no limestones have been 

 noticed in the Lower Beds of the Culm Measures. 



On the high grounds inland, east of Beeny Cliff, angular and sub- 

 angular fragments of cherty rock, derived from the beds beneath, 

 are scattered over the surfaces of the fields ; they are collected, 

 with other loose stones, lor road-material, and as a consequence 

 there are no quarry-exposures. One of these surface-fragments 

 from near Bingford, about 2 miles east of Beeny Cliff, showed in 

 thin section casts of radiolaria; also south of Tresparret Down, 

 about '3 miles east of Boscastle, there were piles of stones, some 

 of them from 2 to 6 inches in diameter, partly of the same dark 

 impure chert as at Beeny Cliff and partly of a light reddish chert, 

 laminated, filled with casts of radiolaria, containing also rhoinboidal 

 crystals, which in microscopic characters closely resemble the 

 typical radiolarian beds of Codden Hill. Still farther eastwards, 

 near Otterham, about 5 miles in a direct line from Boscastle, 

 surface-fragments of dark chert showed numerous radiolaria in thin 

 sections. 



(/) Launceston District, Cornwall. 



The next locality, east of Otterham, where we have met with radio- 

 larian rocks is at Tregeare Down, a hog-backed ridge 718 feet in 

 height, situated between 5 and 6 miles W.N.W. of Launceston. 

 There are on the slopes of the Down three quarries in a north-and- 

 south line ; that at the northern end is small, the beds are mostly of 

 very hard, dark siliceous rock, with a few lighter bands in which 

 radiolaria are readily seen with a lens. The other two quarries 

 are on the south-western slopes of the Down, about \ mile dis- 

 tant from the first. In these the beds are partly of light grey 

 and partly of dark cherty rock, with some soft shaly beds inter- 

 vening. The rocks have been more compressed and disturbed than 

 those in North Devon, and the light shaly beds show indications of 

 incipient cleavage, but, with this exception, they resemble very 

 closely the typical radiolarian rocks of Codden Hill. In the southern 

 quarry the beds dip S.S.E. at 60°. 



About 3 miles east of Tregeare Down, by the side of the high 

 road leading to Launceston, and near the junction of the Lower 

 Truscott Boad, there is another quarry in which the beds are 

 very hard and flinty ; some are black or bluish-black, others 

 grey, and there are also some intervening beds of grey shale in 

 which radiolaria are very numerous. The dip is N.N.W. at 22°. 



