Vol. 5 2. J IN YORKSHIRE AND LINCOLNSHIRE. 197 



the Kimeridge Clay. A. plicatilis, another ' difficult species,' is 

 usually considered an Oxfordian and Corallian form, and under 

 the circumstances the value of the determination is altogether 

 doubtful. These fragments of ammonites are in fact similar to 

 those occurring abundantly in the ' Coprolite-bed ' (E) of Speeton in 

 like preservation, which Prof. Pavlow has studied and illustrated in 

 * Argiles de Speeton ' (pi. ii. & pp. 114 and 115), and considers to be 

 the relics of a fauna not otherwise represented in the section. 

 The species he has identified from Speeton are given in the Table 

 of Cephalopoda facing p. 184. Thus we see that both the composition 

 of the nodules and their fossils tell strongly in favour of their 

 original accretion at their present horizon. 



The weakness of the fossil evidence for their derivative character 

 was evidently felt by the writer of the ' East Lincolnshire ' 

 memoir, who therefore puts forward the further suggestion that ' it 

 is just possible that there were certain older Neocomian beds 

 (destroyed before the deposition of the Spilsby Sandstone), and that 

 some of the casts were derived from them.' But as it will presently 

 be demonstrated that the Spilsby Sandstone represents the lowest 

 horizon of the Speeton Clay (which has been shown by recent re- 

 searches to be older than any known Neocomian rocks and more 

 closely allied to the Jurassic than to the Lower Cretaceous), and as 

 the palaeontological evidence demonstrates that there are no beds 

 missing at this horizon in Lincolnshire which occur in Yorkshire, 

 where, if my reading of the section be correct, there is practically 

 an unbroken record from Jurassic to Upper Cretaceous times, it 

 is difficult to believe that the supposed beds can ever have existed 

 in the area. 



Except in one particular, the nodule-bed of Lincolnshire is indeed 

 in all respects analogous to the ' Coprolite-bed ' of Speeton, the 

 difference being that while the latter occurs as a band in the midst 

 of a conformable clayey or shaly series, and does not mark any 

 striking lithological change, the former is developed along a very 

 important stratigraphical horizon at which the great clayey series 

 of the Middle and Upper Jurassics gives place to the coarse sandy 

 deposit forming the Spilsby Sandstone, a change evidently be- 

 tokening a wide-reaching revolution in the physical conditions of 

 the region. There seems moreover, as already stated, to be 

 evidence of actual erosion and unconformability at this horizon as 

 we approach the Humber, 1 and it is therefore the more remarkable 

 that the nodule-bed should not contain better indications of the 

 destruction of the older strata if any ' pebbles ' were really derived 

 therefrom. But all the arguments which at Speeton a tell in 

 favour of the formation of these phosphatic stones as nodules con- 

 temporaneous with the deposit have equal strength in Lincolnshire. 

 In both districts the stones, though most abundant at a definite 

 horizon, are by no means confined to it, but occur at other levels, 



1 See Geol. Surv. Mem. 1888, ' Country around Lincoln,' p. 82. 



2 Quart. Journ. Geol. Soc. vol. xlv. (1889) p. 584. 



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