Te 
ON THE CRYSTALLINE ROCKS OF ANGLESEY. 129 
but the most valuable part of the analytical work is that which bears 
upon the schistose complex, because of the genetic problems it presents. 
Moreover, that interest is by no means merely local, for similar types 
are found in other metamorphic districts. There is often, in such 
districts, a difficulty in distinguishing schists of igneous from schists of 
sedimentary origin, not to speak of mixed types, which certainly occur. 
In such cases the evidence of the microscope may be inconclusive, and 
resort must be had to chemical analysis. But this is too tedious and 
difficult to be applied with freedom. Every case, therefore, in which 
the mineral composition and microscopic structure of a rock have been 
correlated with its chemical composition constitutes a standard for 
rocks of similar mineral composition and structure. The difficulty is, 
naturally, with the acid schists, and, as Anglesey contains mica schists 
that are, so far as can be ascertained, of both igneous and sedimentary 
ofigin, it is hoped that the evidence that has been gathered in the course 
of the work of this Committee will be of use in the study of the 
crystalline schists as a whole. 
Bembridge Limestone at Creechbarrow Hill.—Report of the 
Comnuttee, consisting of Professor T. McKrnny Huaues 
(Chairman), Mr. H. Woops (Secretary), Dr. J. J. H. TEAL, 
Dr. J. EK. Marr, Professor E. J. GARwoop, Mr. CLEMENT 
Rew, Mr. W. Wuiraker, and Mr. H. A. ALLEN, appointed 
to investigate the Occurrence of the Bembridge Limestone at 
Creechbarrow Hill. 
On the Results of the Further Examination of Cree goa Hill. 
By Henry Keepra. 
In September 1910 I was sent by Professor Hughes to collect fossils on 
Creechbarrow, with a view to determining the age of the limestone 
which caps the hill. In that principal object I was. successful, as I 
obtained a sufficient number of characteristic forms to enable me to 
refer the rock to the Bembridge Limestone. 
The collection is now in the Sedgwick Museum. 
In the report which [ then published 2 I further suggested that 
there was plenty of room for the rest of the Tertiary beds which 
might be expected to occur below’ the Bembridge Limestone, and I 
published a section in illustration of that view. 
I had not, however, then any data to fustify the statement that 
the rest of the Tertiary beds did occur in regular sequence below the 
Bembridge Limestone of Creechbarrow, and therefore confined myself 
to the statement that there was plenty of room for them, as I knew 
them in the adjoining areas, and allowing for such modifications of 
thickness as commonly occurred in the district. 
I regretted leaving the matter in that unsettled state, and applied 
' Geol. Mag., Dec. v. vol. vii., October 1910. 
1D K 
