INFERIOR OOLITE : BRIXWORTH. 185 
Lincolnshire Limestone has disappeared. Hence the structure 
corresponds with that to the south and south-west of Kettering. 
Ironstone has been observed near Irchester and Raunds, but it is 
evidently liable to much local diminution in thickness, for the 
Northampton Sand is not everywhere present along the outcrop. 
This absence may be due to irregular overlap of the Great Oolite 
Series. Northwards along the valley of the Nene and of its 
tributary the Willow Brook, the Lincolnshire Limestone re- 
appears near Southwick and Wood Newton, as a wedge between 
the two Estuarine series, the beds of which, westward and north- 
ward, gradually assume great thickness and importance. 
Prof. Judd further states that "at Wadenhoe, just above the 
level of the river, we have sections illustrating the extremely 
attenuated condition of the Lower Oolites. It is only in very 
good sections that the exact limits between the Upper and Lower 
Estuarine series can be traced, both being often greatly reduced 
in thickness ; wherever a clear section, however, can be traced, 
the ironstone junction-band is morn nr less distinctly exposed, and 
the Upper or Great Oolite beds are found to repose on an eroded 
surface of the Lower or Inferior Oolite beds." He notes the 
succession of strata seen at Wadenhoe, as follows : 
FT. IN. 
Cornbrash - -1 Traceable in 
Great Oolite Clay - > slopes above 
Great Oolite Limestone J the pit. 
"White clays - - 1 
SaS^L**, : : i 8 
White clays, with vertical plant-mark- 
ings - - - - - 9 
T . T?,t - f Dark, carbonaceous clays - 6 
Lower Estuarine I White clays> with vert ical carbonaceous 
I markings and ferruginous stains 2 
Northampton Sand. Ironstone beds, to bottom of pit 8 
Here it is evidently difficult to fix the junction between the 
Upper and Lower Estuarine Series, for the ironstone-band at the 
base of the former has not been noticed. 
Fine sections of the Northampton Sands were exposed at the 
Spratton Ironstone- workings south of Brixworth. 
The following species occur at this locality : 
t Ammonites insignia. ^Pecten. 
f+ jurensis. fTancredia axiniformis ? 
t Murchisonae. fTrigonia compta. 
t opalinus. t v. scripta. 
t Nautilus. tTerebratula trilineata. 
fBelemnites. I maxillata. 
+Pleurotomaria. + (near to) globata. 
JCeromya bajociana. 
* Judd, Geol. Rutland, pp. 98, 99, 143, 169. 
t Obtained by Mr. T. .Tesson, and identified by Mr. E. T. Newton, Geol. Mag. 
1891, p. 493 ; sre also S. S. Buckman, Ibid., 1892, p. 258. Mr. Buckman regards 
one form bere named A. jurensis, as the mutation " Lytoceras Wrighti," and one 
variety or mutation of A. insignis he would name " Hammatoceras Newtoni." 
J Obtained by If. 15. W., and named by Messrs. Sharman and Newton. 
