104 LOWER OOLITIC ROCKS OF ENGLAND : 
palasontological division between the Lias and Oolites, it is of 
course necessary to take the junction between the zones of Ammo- 
nites opalinus and A. jurensis. In order to do this the "Cepha- 
lopoda Bed," as pointed out by Oppel, has to be split into i\\o, and 
consequently some geologists have restricted their application of 
the name to the beds that lie below the zone of A. opalinus. From 
a stratigraphical point of view this is misleading, and it is far 
better to employ the name Cephalopoda Bed in its original sense, 
for all portions of it are so intimately blended that no plane of 
separation whatever can be marked out. 
We find that the sub-zone of A. radians is sometimes placed in 
the lower division of ihe Inferior Oolite, and sometimes in the 
Upper Lias. 
!E. Witcheli* and other geologists have recognized how 
impracticable it is to attempt any precise distinction between the 
upper and lower portions of the Cephalopoda Bed, for it is 
admitted that A. opalinus occurs in the top even of the restricted 
Cephalopoda Bed. 
By uniting into one broad straligraphical division the Cottes- 
wold Sands, together with the Cephalopoda Bed (as a whole), 
we have a group that compares fairly well with the Yeovii and 
Bridport Sands; as both divisions include the zones of A. opalinus 
and A. jurensis, and therefore constitute the passage-beds between 
the Lias and the Oolites. For this intermediate formation the 
term Mid ford Sand is retained, while the name Cotteswold Sands 
is useful locally, as it embraces admittedly only a portion of the 
Midford Sands. 
Ammonites aifrons, or a variety of it (as noted in 1856 by 
Dr. Wright), ranges upwards from the Upper Lias into the base 
of the Cotteswold Sand?, and therefore from a palaontological 
point of view it may be extremely hard to fix any definite 
boundary between the Upper Lias clays and overlying sands.f 
It is true that Dr. Wright suggested that the specimens might be 
derived, but Mr. Buckman is not of this opinion. 
The following grouping is therefore adopted for the bedsj : 
Zones and Sub-zones. 
M'rlf i\ f Gloucestershire Cepha- f Ammonites opalinus. 
1 < lopoda Bed - '\Ji.racKan8 - -] ^ <* 
as< LCotteswold Sands - -/ A. striatulus - - I'^'S 
\ A. variabilis - - J N g 
Upper Lias clays. 
The following fossils have been recorded from the Cotteswold 
Sands and Gloucestershire Cephalopoda Bed : 
* Geology of Strond, p. 34. 
t See Wright, Lias Ammonites, pp. 138, 148; S. S. Buckman, Inf. Ool. Am- 
monites, p. 50. 
J See also Lycett, Cotteswold Hills, p,163; Iludleston, Gasteropoda of Inf. 
Oolite, pp. 60, &c. ; S. S. Buckman, Inf. Ool. Ammonites, pp. 7, 42, 50, 51, 97 ; and 
Quart. Journ. Geol. Soc., vol. xlv. p. 440, vol. xlix. p. 509. 
