40 LOWER OOLITIC BOCKS OF ENGLAND : 
graphical grounds no such separation is wanted. Indeed Dr. 
Wright, seeing the intimate palseontological connexion with the 
beds below, boldly placed the zone of A. opaHnus in the Lias, as 
its highest stage, and in defiance of other authorities.* Such a 
plan, however locally convenient, could not be followed in the 
midland and north-eastern counties. 
We have referred to the assemblages of Ammonites and other 
fossils as serving to indicate a general division between the two 
zones, but the subject is complicated by the differences of opinion 
that exist on the grouping of certain beds and fossils with one or 
other zone ; and the still more serious differences on the identi- 
fication of species the names of Ammonites varying according 
to the " lumping" or " splitting" tendencies of those who assign 
names to them. Hence while one authority gives a wide range 
to a species, another may assign to it a very restricted horizon. 
Thus Mr. S. S. Buckman has pointed out that Ammonites jurensis (as he 
weald define the species) is by no means abundant in this country, the 
species having in some cases been identified from forms which occur at 
higher horizons, and which he would name A confusus and A. Wrigliti : 
both as he admits approach nearly to A. jurensis.^ 
He has subdivided the zones of A. jurensis and A. opalinus into the 
following beds : 
f 6. Opalimis-lteda, with Ammonites opalinus. 
Zones of I 5. Moorei-beds, with A. Moorei. 
A. opalinus J 4. Dmoriena-beds, with A. (Dumortieria} radians. 
and | 3. Dispansus-beds, with A. dispansus. 
A. jurensis. \ 2. Striaiuius-'beds, with A. striatulus. 
[_1. Variabilis-beds, with A. varicibilis. 
This grouping may be taken to indicate the general succession of the 
Ammonite-forms as defined and restricted by Mr. Buckman, but it can 
only be accepted in detail by those who agree with the limitations he 
would assign to the species, and none but a specialist could attempt to 
deal with the subject. 
Including as we do the zone of A. opalinus with the 
Gloucestershire Cephalopoda Bed, and associating with them the 
Cotteswold Sands, we have a group in which Mr. Buckman 
recognizes his six fossil-beds : a group including the zones of 
A. opalinus and A. jurensis. 
In the Bridport and Yeovil Sands we have a group in which 
Mr. Buckman recognizes the zone of A. opalinus and but a 
portion of the zone of A. jurensis ; the other portion being, in his 
opinion, to some extent represented in the Upper Lias shale 
beneath. This view is not at all incompatible with the strati- 
graphical evidence, which shows, as has been pointed out, that 
the lower boundary of the Midford Sands is a gradual one, that 
may vary in horizon from place to place. A similar varying 
junction is met with between Kimeridge Clay and Portland 
* Lias Ammonites, pp. 1, 67, 138, 139, 148 ; Quart. Journ. Geol. Soc., vol. xvi. 
P. 8 ; see also S. S. Buckman, Inf. Ool. Ammonites, p. 253. 
t Inf. Ool. Ammonites, pp. 50, 164, 166; Quart. Joura. Geol. Soc., vol. xixvii. 
p. 601. 
