12 
THE LOWER LIAS OE KEYNSHAM. 
Am. turneri (with the sub-zone of Am. Semico status)^ Am. 
obtusus^ Am. oxynotus. 
The series of indices adopted in this paper is as follows : 
Am. oxynotus 
• .... =Am. oxynotus zone. 
rAm. geometricus ==Am. obtusus and Am. 
Am. arietes 
'Am. semi-1 
costatus 
iAm. 
obliquecostatusi 
Am. bisulcatus 
E,h calcicosta 
Am. angulatus^i Qstrea irregularis 
Echinid Beds. 
rAm. johnstoni 
(Am. planorbis 
Sub- ammonite Beds. 
Am. psilonotus|^ 
Ostrea liassica^" 
Sun Bed 
White Lias 
i" 
1 _ 
turneri 
:Am. bucklandi 
=:Am. angulatus 
:Am. planorbis 
5 = 
=:E,hetic 
0. Uassica zone. 
Since the White Lias and the thick block which caps it 
(the Sun Bed) have, since the time of Moore, been almost 
universally regarded as part of the B-hetic, it is necessary to 
give reasons for including them in the Lias. This we do on 
account of the practical identity of the fauna contained in 
the Sun Bed with that in the sub-ammonite beds imme- 
diately above. The following species are common to both : — 
Ostrea Uassica , Modiola minima^ Pleuromya crowcombeia., 
Lima valoniensis^ Avicula fallax., and Cardium rheticum. 
Of these species Alodiola minima and Avicula fallax are 
found commonly in the Bhetic shales.; Cardium rheticum 
occurs abundantly in the Bhetics, but of a very distinct 
form, which is easily separable ; Lima valoniensis is very 
rare in Bhetic shales, but abundant in the sub-ammonite 
b^ds. The only species which links the Sun Bed with the 
