INFERIOR OOLITE SERIES. 33 
sandy strata in Dorsetshire and Gloucestershire, so that the 
opposition to the term rests very ,'argely on negative evidence, 
which future work may annul. In many instances we have to 
deal with comparatively unfossiliferous sands which afford no 
evidence of any particular zone, but whose general stratigraphical 
position can be proved ; consequently there is need for a stratigra- 
phical term that should include the Gloucestershire Cephalopoda 
Bed and Cottesvvold Sands, the Midford Sands, and the Yeovil and 
Bridport Sands. Paying due attention to the general stratigra- 
phical and palasontological characters of the beds, and to certain 
lithological changes which they undergo, we find that the upper 
limit is on the whole fairly well-defined ; for stratigraphically, in 
Dorsetshire as in Gloucestershire, the zone of Ammonites opalinus 
would be included in this division. In both cases the beds are 
covered conformably by the lower portion of the Inferior Oolite, 
representing the zone of Ammonites Murchisonce. The lower limit 
is nowhere rigidly defined ; and, as is natural with passage-bede, 
the separation of the more sandy from the more argillaceous portions 
would vary in horizon from place to place. From a practical point 
of view it is necessary to represent the essentially sandy beds 
separately from the Upper Lias clay on the maps, and so long as 
the nature of the division is understood, there need be no trouble 
about it. 
As a stratigraphical term, therefore, the name Midford Sand 
may be used in this comprehensive sense, admitting that its lower 
ooundary is one which shades down irregularly into the Upper 
Lias. So far as possible the palajontological characters of the 
beds, and the evidence of different local zones, will be indicated ; 
but, generally speaking, the Midfcrd Sand may be considered to 
include the zones of A. opalinus and A. jurensis, between which 
the division of Lias and Oolites is taken. 
The stratigraphical divisions into which the Inferior Oolite 
Series was originally divided, have proved to be inapplicable to 
other districts in this country. 
In the west of England, we find above the Upper Lias clays, a 
group of sands with bands and nodules of calcareous sandstone 
and occasional shell-limestones (Midford Sand), overlaid by a 
group of oolitic, earthy, and shelly limestones and marls, with 
occasional sandy beds (Inferior Oolite). 
In the midland area, there is no continuance of the gradual 
passage from Upper Lias into the Inferior Oolite Series ; for 
in Northamptonshire and Lincolnshire, though there are occasional 
symptoms of transition, the groups are generally separated by a 
well-marked plane of division, attended by some evidences of local 
erosion. As we pass into these central regions, distinct strati- 
graphical divisions become needful. The iowest beds of the 
Inferior Oolite Series comprise ferruginous sandstones and iron- 
stones, white sand?, and clays, grouped as the Northampton Sand 
and Lower Estuarine Series ; and as we proceed further east these 
E 75928. C 
