INFERIOR OOLITE: HIBALDSTOW BEDS. 221 
Ellerker, the limestone could not be traced as a separate bed, and 
there was no evidence of it in a boring at Brantingham Grange. 
The introduction by Mr. Ussher of the term " Hydraulic Lime- 
stone " for the beds at the base of the Lincolnshire Limestone in 
Lincolnshire is to be regretted, as the layers supposed to represent 
it are not worked for hydraulic lime, and beds on a slightly higher 
horizon (Kirton Beds) are. Nor have we any evidence from 
fossils, for comparing the so-called " Hydraulic Limestone " of 
Lincolnshire with that of South Yorkshire. The latter stratum 
is regarded as equivalent to the Eller Beck Bed, a layer contain- 
ing marine fossils (including Astarte minima), discovered by Mr. G. 
Barrow in the Lower Estuarine Series of the north-eastern part 
of Yorkshire. Moreover, Mr. Ussher grouped the beds termed 
by him " Hydraulic Limestone," with the Basement Beds beneath 
the Lincolnshire Limestone ; but it must be borne in mind that 
the Lower Estuarine Beds of Yorkshire form a more comprehen- 
sive stratigraphical division than the Lower Estuarine Beds of the 
midland counties.* 
The HIBALDSTOW BEDS have been so named by Mr. Ussher 
(1890), because they are well exposed at the village of that 
name, situated between Kirton Lindsey and Brigg. In the 
Geological Survey map (sheet 86), published in 1887, and in the 
Memoir on the Geology of the country around Lincoln (1888 
p. 44) these beds were spoken of as the "Ponton Beds," after 
Great Ponton. But as .the characteristic fossiliferous Ponton 
Oolite cannot be definitely correlated with these beds, and portions 
of the Ponton Beds may be equivalent to the Kirton Beds, it has 
been considered best to adopt purely local names for the divisions. 
As remarked by Mr. Ussher, they form the uppermost division 
of the Lincolnshire Limestone from Waddingham northwards to 
the Humber. They consist of buff or cream-coloured oolites, the 
oolitic structure varying from fine spherical 'to coarse, irregular 
granules, sometimes of large size. These beds do not appear to be 
ever intercalated with clay or loam. Their thickness is probably 
not much more than 20 feet. 
The KIRTON BEDS are so called from the town of Kirton 
Lindsey, in the vicinity of which they present their most marked 
lithological characteristics, and are of the greatest economic 
importance. They consist of grey limestones, interstratified with 
beds of loam and clay ; near Kirton they contain fine-grained 
irregular limestone-bands, which are ground up for hydraulic lime. 
In their lower portion the Kirton limestones, which are partially 
oolitic, frequently resemble the Hibaldstow Beds, weathering 
yellow and exhibiting oolitic structure throughout. 
The Basement Beds form the upper part of the face of the 
Oolite escarpment, the Kirton Beds occupying its crest and the 
upper part of its dip-slope ; these pass under the Hibaldstow Beds, 
which usually make a slight junction-feature at their very sinuous 
* See Fox-Strangways, Geol. Ool. and Liassic Rocks, Mai ton, p. 6 ; Geol. country 
between York and Hull, p. 20; and Jurassic Rocks of Yorkshire, vol. i. pp. 194, 203. 
