LOWER LIAS : POLDEN HILLS. 
79 
Moore's measurements thus give a thickness of 107 ft, 6 in. for 
the basement-beds of the Lower Lias, yielding Ammonites plan- 
orbis : a thickness elsewhere equalled at Rugby and near Carlisle. 
The evidence in this district, if not quite satisfactory, shows 
that these beds at any rate increase greatly in thickness from 
their main outcrop on the west and north-west. It is interesting 
moreover to note the occurrence of the Insect and Crustacean 
Beds, which so closely resemble those of Wilmccte and other 
parts of Warwickshire and adjoining tracts. 
Some of the bands of limestone (16 to 18 feet above the White 
Lias) are much jointed, so as to shatter when struck with the 
hammer, like certain beds in the Lower Lias of Aberthaw ; 
similar beds are seen along the Polden Hills. 
Among the fossils collected at Queen Camel by Mr. J. Rhodes, 
were Hippopotlium (cast), Pholadomya, Rhynchonella, and Wold- 
heimia perforate/. The occurrence of Hippopodium at so low 
an horizon in this part of the country is noteworthy. 
Approaching the Mendip Hills we find the general line of 
outcrop much modified. In the Polden Hills the strike is W.N.W., 
and the beds outcrop towards the south. (See Fig. 84, p. 263.) 
Northwards they occupy a synclinal at Glastonbury, Meare, and 
below Brent Knoll, rising again near the Mendip Hills, although 
not without evidence of faulting. 
In 1860 Dr. Wright published a section of Mr. Cree's quarry 
at Street, observing that he had compared it with the sections 
afforded by the quarries of Messrs. Seymour, Underwood, and 
Talbot in the same parish, and found that the variations in all 
these sections were so inconsiderable, that any one might be said to 
represent the others, both as regards the sequence of the beds and 
the fossils they contain. That this is the case may be seen by 
comparing the section noted by Dr. Wright with that noted by 
myself 25 years later : 
Mr. Cree's Quarry, Street. 
Dr. T. Wright, 1800.* 
Ft. In. 
Mr. Joseph Seymour's Quarry, 
Overleigh, Street, 1885. 
Total depth, about 20 feet. 
Ft, In. 
1. Light-coloured marly clny. Tor 
BED. Saurian bones, Ammonites 
planorbis - - - - 
2. Light-coloured limestone, A. plan- 
orbis .... 
3. Yellowish laminated shale. Ich- 
thyosaurus intermedius, A. plan- 
orbis , Lima punctata, Isastraa 
(latimtsandroidea) 
4. Light-coloured shaly limestone, .4. 
planorbis .... 
.5. Hard grey limestone. BUILDING- 
STONE. A. planorbis, Lima 
punctafa, L. gigantea 
'!. Dark-grey shale, A. planorbis, 
spines of Cidaris - 
7. Dark-grey limestone, CORN-SIZE 
BUILDING -STONE. Spines of 
Cidaris, bones of Ichthyosaurus 
tenuirostris ... 
Thin grey limestone, much jointed. ; 
Brown clay - - - - i 2" 
3 
9 
3 
4 
7 
3 
6 
Pale-bluish limestone. YELLOW 
BED, occasionally used for road- 
metal and paving - - - 
Laminated,shaly play - - 
Limestone. TOP ROCK 
Shale - 
Limestone .. 
08 
3 
-0 9 
Hard blue limestone. CORN SIZE, 
used for building - - - 11 
* Quart. Journ. Geol. Soc. vol. xvt. p. 390; Wright, Lias Ammonites (Palacontograph Soc.), 
of Cree's Quarry, Street, by R. F. Tomes, Quart. Journ. Geol. Soc., vol. xxxiv., p. 1S3. 
