210 LIAS OF ENGLAND AND WALKS: 
contained Ammonites spinatus, Belemnites paxillosus, Pholadomi/a 
ambigua, and Montlivaltia. From blue marl at the same locality 
Moore obtained Ophiodcrma Egcrtoni* 
In the neighbourhood of Rad.^tock and Camerton, there aiv 
beds of iron-shot limestone (with nodules), which yield Gryphcsa 
cymbium, Terebratula punctata, Waldlieimia quadriftda var. 
cornuta, Rhynchonella rimosa, &c., and have been described as 
Middle Lias. The Ammonites however, which include A. armatus, 
A. Jamcsoni, &c., tend to show that the beds belong to the higher 
portion of the Lower Lias, according to the grouping adopted in 
this Memoir. No traces of A. margaritatus and A. spinatus have 
been found in these beds ; but it is possible that here and there 
a layer of stone may be found of Middle Lias age, as in the 
section near Branch Huish, south-east of Radstock, described by 
E. B. Tawney. There the top layer of stone yields Cardinia 
concinna.^ 
Among the beds of the Lower Lias there is, in this area, 
evidence of reconstruction at different horizons, so that, as Moore 
has pointed out, we have presented to us conditions somewhat 
"abnormal," when compared with their "typical" development 
is uninterrupted deposits elsewhere. In his opinion the Mendip 
Hills, although subject to oscillations of level, formed a barrier to 
the incursion of the deeper-sea deposits which were taking place 
to the south. J There may also be evidence of reconstruction 
during the Middle Lias. 
The "nodules" so frequently met with in the limestones, are 
sometimes slightly phosphntic, and appear in many cases to be 
rolled masses of previously formed Lias limestone. 
There is evidence of a considerable thickness of " Blue marl" 
between the Lower Lias limestones and the Inferior Oolite, north 
of Radstock and east of Paulton. A coal-boring sunk through 
the Inferior Oolite on the hill east of Paulton, proved 120 feet of 
" Blue marl." It is highly probable that Lower, Middle, and 
Upper Lias are represented in this group. The evidence tends to 
show that the Marlstone as a Rock-bed is of inconstant occur- 
rence in this area north of the Mendip Hills, as it is in other 
localities ; and it is likely that the main mass of the " Blue marl : ' 
is of Middle Lias age. (See p. 127.) Further north we have 
evidence of blue micaceous marl, beneath a bed of "marlstone," 
at Dundas, where the Upper Lias clay is very thin. 
The section opposite Dundas, given by Moore, is a remarkable 
one, and is unfortunately now obscured: the beds recorded by him 
are as follows : 
* Proc. Somerset Arch, and Nat. Hist. Soc., vol. xiii., p. 150; Quart. Journ. 
Geol. Soc., vol. xxiii. p. 481. 
| Proc. Bristol Nat. Soc., ser. 2, vol. i., p. 186 ; see also I)e la Beche, Mem. 
Geol. Survey, vol. i. p. 280. 
J Moore, Quart. Journ. Geol. Soc., vol. xxiii. pp. 454, 474, &c. ; and Proc. 
Somerset Arch., and Nat. Hist. Soc., vol. xiii. p. 161. 
Proc. Somerset Arch, and Nat. Hist. Soc., vol. xiii. p. 153. 
