486 STKATIGKAPHICAL GEOLOGY 



are about 120 feet thick. They appear to be divisible into three 

 sub-zones characterised by Ammonites which in succeeding order 

 are Hoplites regalis, Holcostephanus speelonensis, and Hole. Decheni. 

 Besides these Crioceras Duvali, Pecten cinctus, Meyeria ornata, and 

 many other fossils occur. The whole of this zone appears to be 

 older than the Atherfield Clay, and is therefore a marine repre- 

 sentative of the Weald Clay. 



The highest part of the Speeton Clay consists of grey and 

 black pyritous clays containing Belemnites brunsvicensis, Hoplites 

 Deshayesi, a large Crioceras, Area securis, Isocardia angulata, and 

 others. These beds are clearly equivalent to the Vectian of 

 Southern England ; their total thickness is more than 150 feet, 

 and may be 180, and they are succeeded by gritty clays of Gault 

 age containing Belemnites minimus. 



In Lincolnshire the Lower Cretaceous Beds emerge from beneath 

 the Upper near Caistor, and extend thence in a gradually widening 

 strip to the neighbourhood of Spilsby and Candlesby at the southern 

 end of the Lincolnshire Wolds. The succession of beds found in 

 this district is shown in Fig. 164, and the full thickness does not 

 exceed 200 feet. 



The Spilsby sandstone has a bed of derived phosphatic nodules 

 at the base resting on the Kimeridge Clay. Above are soft yellow 

 and grey sands, including large masses or doggers of calcareous 

 sandstone, which are rich in fossils and yield Belemnites lateralis, 

 Holcosteph. subditus, Hole, plicomphalus, Trigonia ingens, T. robinal- 

 dina, etc. The Claxby and Hundlesby ironstones also appear to 

 belong to this zone, as they have yielded Bel. lateralis, Hole. Beani, 

 Hole. Gravesiformis, Astarte senecta, Trigonia ingens, Rhynchonella 

 multiformis, Terebratula sella. 



The Tealby Clays are from 40 to 100 feet thick, and represent 

 the zone of Bel. jaculum, yielding that fossil with Hoplites speeton- 

 ensis, Crioceras Duvali, and Perna Mulleti. The Tealby limestone 

 contains Bel. brunsvicensis, Exogyra sinuata, Pecten cinctus, and 

 appears to pass southward into a ferruginous oolitic marl, locally 

 called " roach." Above these calcareous beds is the carstone, 

 which has not yet yielded any fossils except at its junction with the 

 red chalk, where Bel. minimus and Terebratula biplicata occur. 



In Norfolk the thickness of the series is rather less than in 

 Lincolnshire. The Sandringham sands consist of light-coloured 

 sands with some beds of brown flaggy sandstone in the upper part ; 

 they have not yielded determinable fossils, and are not like the 

 Spilsby sands ; hence it is more likely, as Mr. Lamplugh suggests, 

 that they represent the Tealby Clay. The Snettisham Clay 

 contains Bel. brunsvicensis, and appears to be the equivalent of the 



