LOWER LIAS : FEODIXGIJAM. 177 
About a mile and a quarter further north, the Bracebridge 
Brick Company's pit showed, at the base of the Middle Lias 
clays, about 10 feet of clay yielding Ammonites capricornus and 
A. striatus. A trial-boring at Bracebridge was carried to a 
depth of 320 feet without reaching the base of the Lower Lias ; 
saline water was then obtained. (See p. 322.) 
In this area, as elsewhere, the boundary between Middle and 
Lower Lias is very indefinite, as the beds lithologically cannot be 
distinguished. 
Frodingham and North Lincolnshire 
The basement-beds of the Lias (zone of Ammonites planorbis) 
in North Lincolnshire, comprise clays with bnnds of limestone, 
attaining a thickness of 20 feet or more. Remains of Ichthyosaurus, 
Amberleya Chapuisi, Lima gigantca, Modiola minima, Ostrea 
liassica, Pleuromya crowcombeia, &c. have been obtained. The 
beds have been exposed at Scotterwood, west of Scotter, near 
Messingham Mill, and in the low cliff' north of burton-upon- 
Stather. The junction with the Rhaetic Beds is not to be seen in 
section : these beds consist in the upper part of marly shales, with 
on top a band of compact limestone. 
The zones of Ammonites angulatus and A. Bucklandi are repre- 
sented by grey and blue compact and nodular limestones, with 
thicker masses of clay and shale, that form in places a well-marked 
escarpment. West of Frodingham station there is a fine section 
of the beds, which there attain a thickness estimated by Mr. Ussher 
at 170 feet. Iron-shot grains occur in some of the upper beds, 
near the junction with the overlying zone. Gryphcea arcuatu \s 
very abundant. Ammonites Bucklandi, A. Conybearei, Lima 
gigantea, L. Hermanni, Cardinia Listcri, Spiriferina Walcotti t 
and other fossils have been obtained.* 
The beds have been quarried to the south, by the road west of 
Brumby, where they have been opened to a depth of 20 feet. 
Peculiar cup-shaped nodules, or nodules resembling the mouth of 
a funnel, have been observed in these beds in several places by 
Mr. Ussher. 
The most northerly exposure of these strata, is in a quarry 
opposite Whitton pier, where the beds of brown and grey clay 
and limestone were exposed to a depth of 18 feet, beneath a 
capping of gravel. Gryphcsa arcuata and Pentacrinites are 
abundant. Many fossils from this locality were noted 160 years 
ago by J. Wood ward, f 
The most important division of the Lower Lias in this region 
is the J^rodingham Ironstone, a group of ferruginous and fossil- 
iferous limestones, which belong to the z me of Ammonites 
* J. E. Cross, Quart. Journ. Geol. Soc., vol. xxxi. ; and Ussher, Geology of 
North Lincolnshire, &c., pp. 13, &c. 
f Nat. Hist. Fossils of England, vol. i., Part 2, pp. 26, 80, 32, &c. 
E 70859. M 
