20 
LOWER OOLITIC ROCKS OF ENGLAND : 
The Yorkshire term of " Dogger,"* has been applied to the 
representative of the Northampton Sand ; it is a ferruginous 
sandstone, about 5 feet thick. It has yielded a number of 
Lamellibranchs, including Cardium, Corbis rotunda, Cypricardia, 
Isocardia, Modiola sowerbyana, Myojjsis, Pholadomya Heraulti, 
and Thracia ; also the Echinoderm, Galeropygus agariciformis. 
Most of these fossils occur in the Yorkshire Dogger, but they are 
not species that characterize a distinct horizon. 
FIG. 62. 
Quarry west of Ermine Street, near 
the 10th milestone, north of 
Lincoln. (W. A. E. Ussher.) 
.g 
FT. IN. 
5. Brown soil 
with fragments 
of grey lime- 
stone. 
4. Light drab 
loam - - 3 
3. Tough irre- 
gular and im- 
pure lime- 
stone 1 to 4 
2. Drab loam - 10 
1. Hard grey 
limestone - 3 
The Lower Estuarine Beds consist of bluish clay or shale, with 
sand irregularly associated. 
Mr. Ussher states that the divisions of the Basement Beds 
cannot be separated by geological boundaries, as the series forms 
a narrow band on the upper slope of the Oolitic escarpment, and 
its total thickness is insignificant, probably nowhere exceeding 
26 feet. The Lincolnshire Limestone, on the contrary, affords a 
marked contrast in its upper and lower beds, so that a geological 
boundary-line can be drawn from the Humber southwards, to 
separate the Hilbaldstow and Kirton beds. This boundary could 
not, however, be traced very far to the south, owing to the 
merging of these distinctive characteristics, and to the impossibility 
of restricting the variations in the Lincolnshire Limestone to 
definite stratigraphical horizons, f 
The Lower Estuarine Series in the Howardian Hills of York- 
shire contains, in places, towards the middle part, one or two well- 
marked beds of cement-stone or "Hydraulic Limestone." They 
are described by Mr. Fox-Strangways as consisting of hard grey 
argillaceous limestone, never more than a few feet in thickness 
and separating in places into two beds divided by shale. The rock 
can hardly be regarded as an hydraulic limestone, for it is said to 
make " a very good lime for agricultural purposes." South of 
* A name also locally applied to nodular or globular masses of stone, 
f Ussher, Geol. N. Lincolnshire, p. 59. 
