138 Reports and Proceedings—Gilasgow Geological Society. 
chalk, but gives no action with hydrochloric acid. Microscopic 
sections show a fairly transparent ground-mass, apparently amor- 
phous silica, containing granules and subangular fragments up to 
‘075 millim. in diameter, some of which appear to be quartz. 
Besides this, the rock contains numerous radiolaria, and it is really 
a radiolarian earth intermediate in character between the Barbados 
earth and such cherts as those of the Ordovician strata of Southern 
Scotland. 
The details of the extent of the deposit and its relationship to 
other rocks of the area are not yet obtainable, though it is possible 
that a considerable thickness of rock mentioned by Mr. Tenison 
Woods as occurring in this area may also be of radiolarian origin. 
The author describes a species of Cenellipsis, two of Astrophacus, 
one of Lithocyclia (new), one of Amphibrachium, three of Spongodiscus 
(one new), four of Spongolena (all new), two of Dictyomitra (both 
new), one of Lithocampe (new), and two of Stichocapsa (both new). 
From these it is not practicable at present to determine the 
geological horizon of the rock; with one exception, all the genera 
represented occur from Paleozoic times to the present. 
4. “Notes on the Geology of the District west of Caermarthen.” 
Compiled from the Notes of the late T. Roberts, Esq., M.A., F.G.8. 
(Communicated by Prof. T. McKenny Hughes, M.A., F.R.S., F.G.S.) 
To the east of the district around Haverfordwest, formerly de- 
scribed by the author and another, an anticlinal is found extending 
towards Caermarthen. The lowest beds discovered in this anticline 
are the Tetragraptus-beds of Arenig age, which have not hitherto 
been detected south of the St. David’s area. They have yielded eight 
forms of graptolite, which have been determined by Prof. Lapworth. 
The higher beds correspond with those previously noticed in the 
district to the west; they are, in ascending order: (1) Beds with 
“tuning-fork ” Didymograpti, (2) Llandeilo limestone, (8) Dicrano- 
graptus-shales, (4) Robeston Wathen and Sholeshook Limestones. 
Details of the geographical distribution of these and of their 
lithological and paleeontological characters are given in the paper. 
Guascow Gronocicat Socrery, Dec. 8.—Mr. Dugald Bell, F.G.S., 
read a paper “On the Origin of certain Granite Boulders in the 
Clyde Valley.” He referred to the opinion expressed by the late 
Mr. Smith of Jordanhill, many years ago, that a number of these 
boulders around Glasgow had been derived from the neighbourhood 
of Ben Cruachan. With all respect to so eminent an authority, this 
seemed impossible, as according to the evidences of glaciation in the 
intervening district, such boulders would have to traverse at least 
two great sheets of land-ice moving in quite a different direction, 
viz. southward and south-westward, instead of eastward as required. 
Besides, the granite of the boulders referred to is strikingly different 
from the Ben Cruachan granites. Judging from the ice-marks, he 
(Mr. Bell) had long thought that the locality in which these boulders 
originated was to be found in the mountainous tract between the 
head of Lochlomond and the head of Lochfyne. More than thirty 
