INTRODUCTION. 



The 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 limit 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. As a 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. Murchisona, the sub-zone of Am. 

 Sowerbyi, and the zones of Am. 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 



