432 MR, EDWARD GREENLY ON THE [Aug. 1902, 
Now, in a paper on ‘Greenstones associated with Radiolarian 
Cherts,’ > and also in the Geological Survey Memoir on the ‘ Silurian 
Rocks of Britain’ vol. i (1899) pp. 85-87, Mr. Teall has pointed 
out that lavas exhibiting this peculiar pillowy structure have been 
found associated with radiolarian cherts in several parts of Britain, 
in Saxony, and in California, and at several horizons, those in 
California being as late as the Cretaceous.” 
Further, it is known that, in the Southern Uplands of Scotland, 
the radiolarian cherts occasionally pass into the condition of jasper, 
and that this jasper is accordingly, like the chert, associated with 
the pillowy diabase. 
Again, on the South-eastern border of the Scottish Highlands, 
jaspers and cherts are found’ in association with highly-sheared 
rocks of basic igneous origin, though here original structures have 
been for the most part effaced. Radiolaria have been found in 
some of these rocks. 1 have examined specimens of Jaspers from 
both these districts, and could not have distinguished them from 
those of Anglesey. Indeed, I ought to sav that, whereas I had 
been disposed, for some time after going to Anglesey, to regard the 
jaspers as siliceous substitution-products [a view which I find was 
also taken by Prof. G. A. J. Cole*|, the view taken in this paper 
was first suggested to me in 1898 by the fact that my friend, 
Mr. Barrow, at once recognized them as identical in character with 
those on the border of the Highlands. 
If we now compare the photograph (fig. 3, p. 428) with pl. vi, 
p. $31, in the Geological Survey Memoir already quoted, we shall 
see that the jasper at Newborough is not merely associated with, 
but fills the interspaces of, a pillowy diabase in precisely the same 
way as does the radiolarian chert in the Girvan area. Further, 
Mr. Teall permits me to add that, without knowing anything at all 
of the associations of the rock, he wrote to me in 1898 concerning 
a slide which I sent him of a rock from the Pentraeth area: ‘ It 
reminds me of some of the diabasic lavas associated with radiolarian 
chert in the Southern Uplands.’ This rock (Pl. XVI, fig. 1) showed 
the sheaf-like and radial grouping of felspar-laths like that. figured 
by Dr. Ransome” in the Cretaceous diabase of Point Bonita, and in 
several other papers on variolite-bearing pillowy rocks. Finally, in 
the very fine ‘jaspery phyllites’ minute clastic micas can be made 
out, which could not be the case if they were siliceous substitution- 
products. 
No radiolaria, indeed, have been actually found. But thie rocks 
are so much jasperized, even in the most promising localities, that 
1 Trans. Roy. Geol. Soc. Cornwall, vol. xi (1893) p. 560 
2 In the face of an association so world-wide, it seems difficult to avoid the 
conclusion (as suggested by Mr. Teall) that there is a causal connection. 
3 G. Barrow, Quart. Journ. Geol. Soc. vol. lvii (1901) p. 333. 
+ Sei. Proc. Roy. Dublin Soc. n. s. vol. vii (1891) p.114. May not the silica 
which has peugicated the diabase hare been derived from adjacent, and pre- 
existing, jasper ? 
5 Bull, Departm. Geol. Univ. Calif. vol. i (1893) fig. 6, p. 85. 
