170 LOWER OOLITIC KOCKS OF ENGLAND : 
Lincolnshire Oolite Limestone," now generally spoken of as the 
Lincolnshire Limestone.* (See Fig. 112, p. 399.) 
These divisions of Lower Estuarine Series and Lincolnshire 
Limestone, frequently shade one into the other by insensible 
gradations; and occasionally, at their junction, beds of fissile 
sandy limestone occur, which constitute the Collyweston Slate. 
We pass thus from Estuarine Beds to those exhibiting shallow 
marine or littoral conditions, and thence into the somewhat deeper- 
water deposits of the Lincolnshire Limestone. 
The term COLLYWESTON SLATE is adopted from the name in 
common use, in the district between Stamford and Bockingham, 
where " slates " have been worked since the time of Henry VII. 
The chief localities are Collyweston, Easton, Dene, and Kirby. 
The term " Collyweston Limestone and Grey Slate " was used 
by John Farey ;t the earlier name of " Northamptonshire Lime " 
used by Michell in 1788, referring mainly to the Great Oolite. 
The stratigraphical position of the beds, overlying Ironstone and 
Lias, was noted in 1831 by John Phillips. J 
The base of the Lincolnshire Limestone becomes more or less 
arenaceous, and we find a gradual passage through the Colly- 
weston Slate and its equivalents into the Lower Estuarine Series 
below. These junction-beds consist of sands alternating with 
sandy limestones, both often containing concretionary masses. 
The larger forms are known to the quarrymen as " Pot-lids." 
Where these beds become sufficiently fissile, after exposure to frost, 
to be utilized for roofing purposes, they constitute the Collyweston 
Slate : but in many places we find only indurated sandy layers. 
They are from 2 to 10 feet thick. 
These beds, as remarked by Prof. Judd, exhibit ripple- 
markings, worm-tracks, and burrows, and numerous plant- 
remains^ It is most interesting to observe (and the fact has 
been noted by others) || that in lithological characters the Colly- 
weston Slate exhibits nearly all the features of the Stonesfield 
Slate, although it is not so oolitic d,s some of the older beds. 
Moreover there is a striking general similarity in some of the 
fossils, as for instance in the occurrence in both formations of 
Belemnites bessinus. Gervillia acuta, Trigonia impressa, and Pla- 
cunopsis socialis. Vertebrate remains are however comparatively 
scarce in the Collyweston Slate, and no remains of Insects and 
Crustacea have been recorded from it ; although a few specimens 
of Saurians and Crustacea have been obtained from the North- 
ampton Sand. One of the most characteristic fossils of the 
Collyweston Slate is the Gasteropod, Malaptera (Pterocera) 
Bentleyi* 
* Geol. Kutland, pp. 33, 90, 140. 
t Agric. Derbyshire, 1811, p. xxix ; and Supp. Index to So-vrerby's Mineral 
Conchology, vol. i. 1815. 
J Geikie, Life of Murchison, vol. i. p. 1 82. See also Brodie, Proc. Cotteswold 
Club, vol. i. p. 53. 
Geol. Kutland, pp. 140, 157. 
|| J. Phillips, Geol. Yorkshire, Part 1, ed. 2, 1835, p. 131. 
