S. Sharp — On the Northampton Oolites. 447 



Upon the foregoing beds I will remark briefly : 



1. The White Limestone is disposed in beds from a few inches to 

 about three feet in thickness, much fissured, and contains character- 

 istic Great Oolite fossils. It is traversed by an earthy zone of from 

 9 to 18 inches thickness, made up of thin lamina, and containing 

 flattened bivalves, which are well preserved. This limestone passes 

 down into — 



2. Blue and Grey Clay. This clay is used in many places for 

 brick-making. At Kingsthorpe, at the base of the limestone, is a 

 zone containing Bhynchonella concinna and Modiola imbricata in abun- 

 dance, and these are found also in the underlying clay to the depth 

 of a few inches. In the same section a zone of Ostrea Soioerbyn 

 occurs in the limestone ; in some other localities these same forms 

 occur in the clay beneath. This clay passes down by an easy transi- 

 tion into — 



3. White clayey sand, with occasional ferruginous stains. In 

 some places this sand has become so indurated as to be used as a 

 building stone, and has proved very durable. Few fossils occur in 

 this sand, but at its base there occurs a plant-bed, composed of 

 thin alternating layers of sand and vegetable matter of a thickness of 

 from 6 to 12 inches, overlying a band containing root perforations 

 running down to a depth, in some instances, of two feet. Conform- 

 able to these sands is — 



4. A series of very variable beds, composed sometimes of fer- 

 ruginous sandstone, in thin layers which overlie calcareous beds con- 

 taining shelly zones and plants, false bedding being frequent. 

 Sometimes the whole section presents a series of beds of compact 

 ferruginous sandstone, with no fossils — an excellent building-stone ; 

 in one instance the entire section consists of white sand and sand- 

 stone. Near the bottom of the beds there occurs in some localities 

 a zone of coral, composed chiefly of Thamnastrea. 



Immediately beneath these beds I have placed, as above, the 

 Stonesfield slates, not in accordance with any conclusion arrived at 

 by myself, but iipon information derived from certain geologists 

 whose opinions are worthy of all respect, and whose aid, together 

 with that received from time to time from other geological friends, 

 I will take a future opportunity of more particularly acknowledging. 



5. A coarse shelly Calcareous Oolite. I will here content myself 

 with saying that this bed is in texture much like some of the Stam- 

 ford limestones, and, like them, it contains Inferior Oolite fossils — 

 Lima granclis, etc. Associated with this bed is — 



6. An Arenaceous Slate-bed, worked anciently for roofing slates, 

 and which, because of its position with reference to beds above and 

 below it, I have for some years held to be equivalent to the Colly- 

 weston slates, and with the latter to belong to the Inferior Oolite 

 series. What little merit may be due for such identification, I think 

 I may claim. Immediately under, and conformable with, this slate- 

 bed are the interesting — 



7. Ironstone-beds. These are so variable in thickness that, though 

 at Kingsthorpe they are represented by a bed one foot thick, at 



