124 LIAS OF ENGLAND AND WALES I 
appears also in numerous excavations, forming a thick horizontal 
bed, reposing on ochreous sand. The whole surface is often 
scarred with deep, conical, and often very extensive hollows, 
which probably are ancient ochre pits." Weaver mentioned that 
beds of clay, from 1 to 3 feet thick, and much charged with 
yellow ochre, were wrought for the sake of that substance (from 
which a pigment was prepared), by means of pits sunk two or 
three fathoms in depth. Some of these pits, however, may have 
been sunk to obtain calamine from the Dolomitic Conglomerate 
beneath the chert, while others may be natural vt pot-holes " or 
" swallet-holes," due to dissolution of the Carboniferous Lime- 
stone. It is difficult in every case to decide the origin of the 
pits, for most of them are much obscured by a talus of chert and 
sandstone fragments. 
The largest and most instructive pit occurs east of the Harptree 
Road, about half way between East Harptree and the Castle of 
Comfort. It is about 60 feet in diameter at the mouth, is funnel- 
shaped, and about 20 to 30 feet in depth. It is evidently a 
natural ''pot-" or " swal let-hole." The section consists almost 
entirely of massive bedded chert, occurring in layers of from 1 to 
3 feet in thickness, standing out sharply, but sometimes weather- 
ing sandy at the exterior, and separated by thin clayey beds an 
inch or two in thickness. The beds are coated here and there 
with quartz crystals. 
Most of the ochre appears to have been obtained from beds at 
or near the base of the chert. The chert itself is often of a com- 
pact character, and sometimes banded, resembling the rocks 
termed Hornstone and Woodstone by the older Mineralogists. In 
other instances the texture is granular. It is of various shades of 
brown, buff, bluish-grey, and white; and associated with it are 
beds, described by Weaver as quartzose sandstone. The rock- 
specimens examined by Mr. Teall, including the granular varieties, 
consist of chalcedonic silica. Heavy Spar occurs here and there 
in the joints of the rock. 
A number of fossils were collected by R. t Gibbs and myself 
from the chert of Harptree Hill ; and in the large pit (before 
mentioned) fossils were noticed only in the upper beds, and these 
were extracted with great difficulty. Specimens are more readily 
to be obtained from loose blocks, or from the walls, where the 
rock has to some extent decayed and become softer. The 
following species were identified by Mr. Etheridge* : 
Ammonites planorbis. 
Johnston!. 
Astarte, sp. 
Cardinia suttonensis. 
sp. 
Lima gigantea. 
pectinata. 
pectinoides (like L. duplicata). 
cast of, like L. exaltata. 
Modiola minima. 
Pleuromya. 
Myoconcha psilonoti. 
Ostrea liassica. 
multicostata. 
sublamellosa. 
Pecten Pollux (or suttonensis). 
Unicardiuro. 
* Geol. E. Somerset, &c., r p. 108. See also Moore, Quart. Journ. Geol. Soc., 
Tol. xxiii. p. 492. 
