76 GASTEROPODA OF THE INFERIOR OOLITE. 
interior the fawn-coloured sandy limestones of the Howardian Hills, worked in 
Whitwell parish and elsewhere, are referred to this horizon. North of Scar- 
borough, on the coast, 100 feet of “‘ estuarine’ sands and shales, containing the 
principal moorland coal and the celebrated plant-bed, intervene between the 
Millepore-bed and— 
3. The third zone, known as the ScarsoroucH or Grey Limestone. South of 
Scarborough these two zones approach each other—the Millepore-bed, as we have 
seen, becoming thicker, whilst the Scarborough Limestone in Gristhorpe Bay is 
reduced to a few feet, with every indication of going out altogether. Thus itis the 
Millepore-bed which reappears further south as the Cave Oolite and the Lincoln- 
shire Limestone. Near Scarborough, however, and especially north of that town, 
the uppermost of these two formations is far the most important. On the south 
horn of Cloughton Wyke, at Hundale, this group of beds has a thickness of nearly 
60 feet, and contains a fine series of fossils, chiefly Conchifera. On the other 
side of Scarborough, at White Nab, the thickness has already fallen to 20 feet. It is 
here that specimens of Am. Humphriesianus and Blagdeni have been found together 
with casts of a large Pseudomelania and Phasianella. Lithologically this zone 
is composed for the most part of blue-grey limestones, more or less charged with 
dark-coloured mud, and in places is rich in iron. The fossils partake of this grey 
character, but there is a little difficulty sometimes in distinguishing specimens from 
certain varieties of the Millepore-bed or Cornbrash. This is the least oolitic in 
structure of all the four zones of the Lower Oolites. 
The three zones enumerated above belong to the Inferior or Bajocian subdivision 
of the Lower Oolites. The two lowest (i.e. the Dogger and the Millepore) are 
probably both in the Murchisong-zone, though no Ammonite has ever been found 
to my knowledge in beds of this horizon on the coast. The Scarborough Lime- 
stone, which distinctly dies out on the dip, must be regarded as on a level with 
the Coronaten-zone of the Germans. Above this comes a third “ estuarine” 
series, which also thins considerably on the dip. As we have no paleontological 
indications in Yorkshire either of the Parkinsoni-zone or of the Great Oolite, it is 
not unreasonable to suppose that this third estuarine series may represent these 
formations in time. The gradual attenuation of the Great Oolite (Bathonian) in 
Lincolnshire as a marine formation prepares us for this change. 
We have no difficulty in regarding both the Dogger and the Millepore-bed as 
belonging to the Lower Division of the Inferior Oolite, but with respect to the 
marine beds, known collectively as the Scarborough or Grey Limestone, the 
case is not quite so clear. It is perfectly true that south of Scarborough Castle 
Ammonites of the Humphriesianus-zone are found; but the fossiliferous exposures 
of Cloughton Wyke, both at Hundale Point, and also the one high up in the cliff 
on the opposite side, usually known as Pickering Cliff, have never tomy knowledge 
