Prof. Hughes—Lower Cambrian, Bethesda, N. Wales. 11 
a name much in people’s minds at the time it was opened. In this 
quarry the new Trilobite, Conocoryphe viola, Woodward, was found 
by Mr. Lloyd. I verified its occurrence by finding several specimens 
myself. I have been able to add also another smaller species of 
Trilobite, but my specimens are too fragmentary for determination. 
There is also not uncommon in these beds a rounded pear-shaped 
body, with a granular texture and banded structure, perhaps some 
form of sponge. There are hardly any indications of bedding, except 
the regular roof of grit and the constant but less regularly occurring 
purple slates below. There are a few sandy lines and bands, which, 
however, can rarely be followed for more than a foot or so. The 
fossils appear on distorted bed faces, generally lying within 5° or 10° 
of the cleavage planes. 
These beds are locally known as the Upper Green Slate, Maenty- 
gwyrdd uchaf, or Cerrig Ilwydion, and the estimated thickness 
is 120 feet. 
The Upper Green Slate passes down into the next subdivision. 
b. Purple Slate. The way in which this comes on shows that the 
colour does no go for much, as it occurs in a blotchy irregular 
manner, suggestive rather of local circumstances affecting the iron 
in the rock at any time subsequent to its deposition. It has often a 
silky texture; this character being seized upon by the workmen, 
who called it the Silky Vein, or Cerig Rhiwiog, as distinguishing it 
from the more sandy and irregular mass of slate below. It is of 
about the same thickness as the Upper Green Slate, viz. some 
120 feet. 
c. A coarser and less evenly cleaved rock which is called Bastard 
slate, and is said to be in thickness about 850 feet. 
d. The old blue slate, so called first because it was one of the 
earliest quarried, and next because of its colour. The colour is, 
however, more green than what we should understand by blue 
when applied to a slate. This difference is lost in the Welsh name 
Careglas.. It is in the upper part of this band that the traces of 
fossils have been recently found in the working known as 
Sebastopol, according to Mr. Lloyd’s estimate, some 1200 feet lower 
than the Crimea quarry, or zone of Conocoryphe viola. 
e. A bed of red gritty rock, known as Gwenithfaengoch, about 
16 feet in thickness, separates this slate from 
_ jf. The Lower Purple Slate, Cerig Cochion, which attains a thick- 
ness of 300 feet, and passes down through 
g. About 240 feet of veined slate, known as Cerig gleision 
gwythienog, into 
h. The Lower Green Slate, Gwyrdd isaf, in which there is some 
300 feet of workable slate. 
H. Greenish sandy beds, with included fragments of older rock, 
are just touched at the bottom of the quarry. These are probably 
the top of the passage beds into the schistose fragmental rock, 
which is associated with 
K. The cleaved grit and conglomerate, seen near the bridge, south 
of Bethesda. 
