3G 
LIAS OF ENGLAND AND WALES : 
These beds have been subdivided into Zones which may be 
conveniently grouped as follows : 
GENERAL 
GROUPING. 
ZONES. 
CHIEF LITHOLOGICAL CHARACTERS. 
Ammonites 
capricornus. 
A. Jamesoni 
A. oxynotus 
A. Bucklandi 
A. planorbis 
Ammonites capricornus 
and A. Henley i. 
A. Ibex 
A. Jamesoni 
A. armatus 
A. raricostatus 
A. oxynotus 
A. obtusus 
A. semicostatus and A. 
Turneri.*' 
A. Bucklandi 
\ A. angulatus 
I A. planorbis 
Clays with reddish-coloured ironstone 
nodules. 
}Dark clays and pyritic shales, with 
occasional sandy beds, and ironstone 
nodules. 
}Dark clays and shales, with much iron- 
pyrites. 
1 Blue argillaceous limestones and clay 8 
I mainly clay or marl in some 
| localities and with ironstone at 
J Frodingham. 
Even-bedded limestones and shales, pale 
marly limestones and fissile marls. 
These are the broad general divisions that may be traced across 
the country, and throughout it the chief zones have been 
identified, though in many localities, owing to the absence of 
sections, particular zorlea have not at present been distinguished. 
Nowhere in the Lower Lias is there any marked band of rock 
that can be traced persistently for any great distance. Generally 
speaking the lithological characters assigned to the zones are 
fairly persistent, but there is no sufficiently definite association of 
beds of particular lithological character, such as would enable us 
to fix horizons independently of organic remains. Some of the 
" Insect limestones " in Warwickshire, and adjoining parts of 
Worcestershire and Gloucestershire, present characters that enable 
us to identify the division to which they belong, and it will be 
seen that the great masses of limestone, wherever they occur, 
belong to the lower part of the Lower Lias : but the great 
developments of limestone, belonging to the zones of Am. angu- 
latus and A. Bucklandi, such as we see at Lyme Regis, near 
Bridgend, at Harbury and liugby, are more or less local, passing 
elsewhere into clays with occasional bands of limestone. Higher 
up the dark pyritic shales are suggestive of beds belonging to the 
zones of Am. oxynotus or A. armatus, &c., while clays with 
ochreous nodules are suggestive of the zones of A. Jamesoni and 
A. capricornus. This argillaceous division is for the most part 
well developed, excepting in the neighbourhood of RadstocK in 
Somersetshire, where some of the subdivisions are represented by 
single bands of limestone. 
* Wright considered the zones of A. Turneri and A. semicostatus as the upper 
Dart of the zone of A. Bucklandi. Lias Ammonites, Palseontograph. Soc., pp. 284, 
286. 
