Dr. C. Callaway—Pre-Cambrian Geology of Anglesey. 119 
B.—ContTInvuIty OF THE GRANITOID SERIES WITH AN UNDERLYING 
GNEISS. 
(a). The Craig yr Allor anticlinal.—Dr. Hicks! states that the 
Dimetian granitoidite is the “base-line or axis” of the Pre-Cam- 
brian rocks of Anglesey. From this conclusion I am compelled to 
differ. I do not here discuss the details of the group or groups 
which underlie the Dimetian: I am only concerned to prove that-it 
passes down without a break into a great schistose series. The 
Fic. 1.—Plan of the Craig yr Allor anticlinal. 
Scale: One inch to the mile, 
— eS = 
- 
ae. K 
Bays 
4 
4 
4 bias 
©. Brefor 
Pid shes 
Ci legyr/gwgtaon 
A 
ts: Lilechyn farwy 
J ! 
Cwynly! 
/ “Ny 5% 
/ 
/ 
ot yrewydd 
/ Or 
! eis 
! 
(es 
\ 
\ 
\ 
\. Bwleyn Je? Hol hes 
\ ce 4 J head fioad 
artes : Gwulehmar 
The arrow-marks indicate dips of dark gneiss. The dotted line is the boundary 
between the gneiss and the granitoidite. 
evidence of this statement is absolutely complete. In the very 
centre of the granitoid “axis,” rises a dome of dark gneiss, throwing 
off the granitoidite in all directions, and passing up into it through 
beds of an intermediate lithological character. This dome is ellip- 
tical, and is three and a half miles long by about one mile and a 
half broad, its larger diameter striking north-east in agreement with 
the general strike of the district. It lies mainly north of the Holy- 
head Road, and is represented, in part, by the patch coloured as 
1 Quart. Journ. Geol. Soc, vol. xxxy. p. 302. 
