274 
LIAS OF ENGLAND AND WALES: 
facts are interesting as affording some evidence of a local break in 
the zone of A. jurensis. As Mr. Thompson points out, sandy 
conditions came on earlier in the west of England than in the 
midland counties, and the general assemblage of fossils met with 
on the same horizon would be liable to the variation due to 
different conditions of the sea-bed,* (See also p, 246.) 
To the north-east of Banbury the lower beds of the Upper 
Lias have been exposed in numerous sections, which have been 
described by Prof. Green, f Mr. Beesley,J Mr. E. A. Walford, 
and Mr. Beeby Thorn pson.|| The sections are of interest as 
furnishing evidence of the " Transition Bed " before mentioned, 
that occurs between the Middle and Upper Lias. Sections have 
been opened up near Chacombe, Middleton Cheney, Thenford, 
Hellidon, and other places. There the Basement-Beds of the 
Upper Lias consist of clays and white earthy limestones, varying 
a good deal in detail, from 6 to 9 feet thick, and yielding the 
usual Ammonites. At Thenford some Fish-remains were ob- 
tained by Mr. Beesley, but the various fossil-horizons have only 
locally been identified. (See Fig. 88.) 
FIG. 88. 
Section in a Quarry South of Thenford, Northamptonshire, 
'(Prof. A. H. Green.) 
A. Surface-soil and Rubble. 
B. Marlstone Rock-bed. 
C. Upper Lias clay?, with, two beds of earthy limestone, 
x Fault. 
In the higher part of the Ouse Valley the outcrop of the 
Upper Lias occupies an extensive tract, being a portion of the 
main mass which skirts the Cherwell valley to the south-west. 
Details of one or two sections will be sufficient to indicate the 
characters of the beds seen in this district. 
* Journ. Northamptonshire Nat. Hist. Soc., vol. vi. p. 99. 
f Geol. Banbury, p. 8. 
j Proc. Warwickshire Field Club, 1872, p. 23. 
See references on. p. 228. 
j| Jouru. Northampton Nat. Hist. Soc., vols. iii. to vi. 
