INTEODTJCTION. TU 



J. Sowerby [ = Am7no)iifes jason,liemecke, s^)., ^de Oppel). Many other species of 

 Cephalopods have been collected in the beds by Mr. Thurlow Leeds and others, the 

 most important being Cardioceras lamherti, C. serratum, Cosmoceras spinosum, 

 C. duncani, C. ornatuvi, Peltoceras atlileta, P. wilUamsoni, var., Asjndoceras per- 

 armaUim, Quenstedtoceras maricB, and Belemnites oweni. 



The horizon at which these forms occur is described by English stratigraphers as 

 the Lower Oxford Clay *. By continental geologists strata of the same age would be 

 called Upper, or Middle and Upper Callovian, but, as Mr. H. B. Woodward f has 

 remarked in the memoir referred to below, "This seems a quite unwarranted stretching 

 of a formation to suit local stratigraphy and in defiance of its original significance." 

 Accordingly the horizon in which the reptilian remains are found is here called the 

 Lower Oxford Clay (Middle Oxfordian). The general succession of the beds of this 

 age in Northamptonshire has been described by Prof. J. W. Judd ;|; under divisions b-e 

 as follows : — 



(/) Zone of Ammonites cordatus. 



(e) Clays with Ammonites of the group o£ the Ornati. 



Dark blue clays with nodules o£ pyrites and numerous pyritic Ammonites, including 

 A. ornatus, A. duncani, A. lakci'ice, and A. athleta, and also Waldheimia 

 imjyressa. 

 Dug in brickj-ards about Whittlesey^ at Thorney, and Eye Green. 



[d) Clays with Belemnites hastatus. 



i51ue clays with many fossils found in Division c, but characterised by the 



abundance of B. hastatus. 

 Dug at Werrington, Ramsey, and Eyebury. 



(c) Clays with Belemnites oweni. 



Dark blue clays and shales with B. oweni, often of gigantic size. Gri/pluea dilatata 

 occurs, but is more plentiful in the beds above. Saurians and fishes occur^ and 

 masses of lignite, sometimes converted into jet, are found. 



Exposed in brickyards at Standground, Fletton, and Woodstone, near Peterborough, 

 and at Connington, Luddington, and Great Gidding. 



(6) Clays with Nucula. 



Laminated blue shales with compressed Ammonites and Nucula nuda. 



Dug at Haddon, HolmCj south of Peterborough, and at Eyebury to the north-east. 



(a) Zone of Ammonites calloviensis. 



* See 'Memoirs of Geol. Survey of the "United Kingdom — The Jurassic Eocks of Britain,' vol. v. "The 

 Middle and Upper Oolitic Eocks of England," by H. B. Woodward (1895) p. 8. 



t Tom. cit. p. 9. t ' Geology of Eutland ' (1875) p. 232. 



