STRUCIURE OF SOME SHROPSHIRE ROCKS. 669 
clude, from microscopic evidence alone, irrespective of that obtained 
in the field, that the granitoid series was much older than the other 
rocks, and that materials from it, together with fragments from the 
rhyolitic series, had been worked up into several of the later clastic 
rocks. It is remarkable that we find herein Salop, as in Caernavon- 
shire, a metamorphic group and a felsitic group (with considerable 
similarity in each case) in apparent sequence, yet with marked 
difference in age. Some of the Primrose-Hill specimens also rather 
resemble certain other rocks recently described by Dr. Hicks, more 
especially from St. Davids*, and by him grouped with the Welsh 
quartz-felsites under the name Arvonian, 
Discusston. 
Dr. Hicks spoke of the extreme interest of the paper, and the 
confirmation it furnished of the views he had already expressed. 
He thought that probably at least three groups would be found in this 
region also. It was also interesting as showing that the granitoid 
series had a different strike to that overlying it. 
Prof. Hueuxs wished to ask if the stratigraphical relations of the 
rhyolite and the granitoid rock had been observed in the field, or 
were only inferred from microscopic examination ; and whether the 
discordant strike had been observed on the same side of the fault. 
Prof. Bonney said the rhyolite was clearly intrusive in the grani- 
toid series; and mentioned some points of interest connected with 
the microscopic examination of the rocks, which he had described in 
an appendix to Dr. Callaway’s paper. 
Dr. Cattaway said that he had only been able at two or three 
places to see the granitoid and rhyolitic rocks in contact, and in all 
cases they seemed to be separated by faults; but there could be no 
doubt that the granitoid was the older. He had not at present 
been able to recognize more than two series. 
* Quart. Journ. Geol. Soc. vol. xxxy. p. 285. 
Q.J.G.8. No, 140. 2% 
