228 LIAS OF ENGLAND AND WALES : 
On Burton Dassett Hill there are large quarries in the Marl- 
stone. On Bitham Hill which rises to a height of about 690 feet, 
the rock is very ferruginous ; and siliceous iron-ore also occurs 
in the outlier of Northampton Sands at this locality.* 
North-east of Banbury, at Chipping Warden, Aston-le-Wall, 
and other localities, in Oxfordshire, Northamptonshire, and 
Leicestershire, a remarkably fossiliferous bed occurs at the 
junction of the Middle and Upper Lias. This was termed the 
Passage-bed in 1872 by Mr. T. Beesley,t who first found in it 
Ammonites acutus, a species described by Prof. Tate.J 
In 1878 Mr. E. A. Walford, applying the term " Transition- 
bed," gave detailed accounts of the sections, and a long list of 
species obtained from the bed ; and subsequently it has been 
examined and described in many places by Mr. Beeby Thompson. 
Mr. E. Wilson, and Mr. W. D. Crick. 
The bed consists of grey friable marl and marly limestone from 
1 to 9 in. thick, and from the local abundance of Ammonites 
acutus it might have been termed the zone of that fossil, although 
the species occurs both above and below the particular horizon. 
Mr. Walford observes, " We may regard it as a Transition 
bed from the Middle to the Upper Lias, though for purposes of 
classification, taking Tate and Blake's divisions as our standard, 
from a preponderance of medio-liassic forms it may be placed as 
the uppermost member of the Middle Lias, and hence perhaps 
synchronous with Tate and Blake's zone of Ammonites annu- 
latus. r ' As the zone of A. annulatus is generally regarded 
as the base of the Upper Lias, we should most properly group 
the Transition Bed with that formation. It is, however, more 
convenient to consider it with the Middle Lias. 
Its comparative insignificance is quite consistent with the 
notion that to some extent, when present in a friable condition, it 
may be clue to the decomposition of the underlying rock, while the 
frequent abundance of organic remains may in this, as in other 
cases, be the result of some pause in the deposition of sediment. 
The following section, seen in a pit about a mile north of the 
church at Chipping Warden, gives the general characters of the 
beds. I was conducted to the spot by Mr. Walford who has 
given the following description || : 
FT. IN. 
Soil - - - - 1 6 
("Grey clay with interrupted band of white 
Upper Lias. I limestone, with Ammonites crassus, &c. - 22 
| Limestone in two bands (Fish-bed), with 
L Fish-remains, Euomphalus (?) minutus, &c. 3 
* Hull, Explanation of Hor. Section, Sheets 71 and 72, p. 5. 
| Proc. Warwickshire Field Club for 1872, 1873, pp. 18, 23. 
I Geol. Mag. 1875, p. 204. 
Proc. Warwickshire Field Club for 1878, 1879 ; and Journ. Northampt. Nat. 
Hist. Soc., 1883, p. 296. See also Beesley, Proc. Geol. Assoc., vol. v. p. 167. 
|| On some Middle and Upper Lias Bels in the Neighbourhood of Banbury, Proc. 
Warwickeh. Nat. Club, 1878, Reprinted Banbury, 1879, p. 6 ; see also Notes on 
some Polyzoa from the Lias, Quart. Journ. Geol. Soc., vol. xliii. p. 632 ; and B. 
Thompson, Rep. Brit. Assoc. for 1891, p. 334. 
