INTRODUCTION. 
Tue vertical limits of the Inferior Oolite in England, as far as the Gasteropoda 
are concerned, lie between the Fuller’s Earth, where that series is developed above, 
and the Upper Lias below. By some authorities the Fuller’s Earth has been 
regarded as pertaining more to the Inferior than to the Great Oolite. Very little 
seems to be known of its Fauna, but its argillaceous character serves to connect it 
more with the Great Oolite than with the Inferior Oolite. Be this as it may, 
there are so few Gasteropoda that the inclusion or exclusion of the Fuller’s Earth 
within the assigned limits is a matter of very little consequence. Further north, 
where the Fuller’s Earth altogether fails, the upward boundary becomes a little 
indefinite for a time, especially in North Oxfordshire, &c.; but, fortunately, these 
doubtful beds contain very little bearing upon our subject. In Northamptonshire 
and Lincolnshire the uppermost beds of the Lincolnshire Limestone must be 
regarded as the upper lmit of the Inferior Oolite in that direction, and this 
arrangement carries us to the Humber. In Yorkshire the Scarborough or Grey 
Limestone is the highest bed of Inferior Oolite age which is known to contain 
marine fossils. 
Turning now to the lower boundary there seems to be a general opinion that 
the Sands of the Inferior Oolite should be restored to their old position as part of 
that series, which will, therefore, include the Cephalopoda-bed of the Cotteswolds 
and its Dorsetshire equivalents. Asa matter of fact there are but few Gasteropoda 
in sufficiently good condition in these essentially transition beds between the Lias 
and the Oolites to make their acquisition of much value, and consequently but few 
specimens are likely to be selected for description from them. 
The main mass of the Gasteropoda of the Inferior Oolite is to be found in the 
various limestones, more or less oolitic, and sometimes irony and arenaceous, 
which lie between the equivalents of the Gloucestershire Cephalopoda-bed and 
the base of the Fuller’s Earth. Portions of this region constitute a really rich 
hunting ground, and, where the whole is fully developed, include three, if not 
four, well-known life zones, viz. the zone of Am. Murchisone, the sub-zone of Am. 
Sowerbyi, and the zones of 4m. Humphriesianus and Am. Parkinsoni. These zones 
or life horizons are not made out with equal clearness in all places, partly, perhaps, 
from local causes of obscuration, but mainly, I am inclined to think, from the 
