100 PROF. GROOM ON THE CAMBRIAN AND [ Feb. 1902, 
horizon evidently below that of Peltura. Suspecting the presence 
of shales at the north-western corner of Chase-End Hill, I caused 
excavations to be made which resulted in the discovery of Black 
Shales (M 257) interbedded with thin bands of coarse, very dark- 
grey quartzose grit and invaded by one or two sills of igneous rock 
(M117). The series constitutes the 
Lower Igneous Band. The 
grits vary from seams a fraction 
of an inch thick to bands 8 inches 
thick. Like the Hollybush Sand- 
stone, they contain glauconite, but 
are generally appreciably coarser 
than the black and dark-grey 
varieties of that formation. The 
shales at this point are in contact 
with the Hollybush Sandstone, 
but the actual junction is obscured 
by the decay of the rocks on either 
side. The dip of the shales is 
uniformly high, and varies about 
10° on either side of the vertical. 
Lithologically the shales are indis- 
tinguishable from other portions 
of the White-Leaved-Oak Series. 
The thickness of the series, ex- 
clusive of the sill M117, is about 
30 feet (fig. 2); but it is possible 
that higher shales belonging to 
the same series occur south-west 
of this sill. A complete lack of 
exposures, however, precludes an 
examination of the beds for some 
distance in this direction. 
Excavations over the whole 
outcrop carried on for several 
days, with the aid of a man and 
S.W. 
Black Shales and grits, with Polyphyma 
The dip of the sandstone is doubtfully 
D7 
A: Shales at the northern evtrenuty of 
Zi 
nd Hill. 
I 
Supposed fault. 
7 
ty 
F= 
1 inch = 16 feet.] 
Chase-1 
[Seale : 
Hb.8 = Hollybush Sandstone with M 117 (olivine-basalt); M 
tx 
M 117b 
AMR gs 4 
Aish | 
. 
yf Hollybush Sandstone and Blac 
ates \ 
~) fhe 
=? - 
Lapworthi; M117 = Hornblende-camptonite. 
ES boys, resulted in the discovery 
= of perhaps a thousand fossiliferous 
s j 
3 n , fragments, many of which showed 
Ry = aD . 
B = = a number of fossils. The pre- 
| 2 vailing fossil is Polyphyma Lap- 
N a worthi, Groom,' a fossil which is 
= = probably allied to ‘ Beyrichia’ 
= 2 Angelini, Barrande, and of which 
several hundreds of recognizable 
individuals were obtained. These 
were associated with a much smaller number of a small ostracod 
somewhat resembling Leperditia. Some of the layers are very 
rich in the remains of hexactinellid sponges, most or all of 
1 Quart. Journ. Geol. Soe. vol. lviii (1902) p. 83. 
