NEOCOMIAN. 143 



120 feet of clay in which there is a large number 

 of characteristic Ammonites, with species of Tere- 

 bratula and Rhynchonella. The third zone is that 

 of the Belemnites semi-canaliculatus. In this zone 

 in the Ammonites Deshayesii found in the Lower 

 ensand of the south of England. The upper- 

 most Eone of the Speeton clay is that of Belemnites 



minimus. This fossil which in the south of Eng- 

 land abounds in the Gault, here occurs in aS 



with Tnoceramx tntricus^ Inoceramus 



sulcatus and Nucula pectinata^ which are also com- 



I ilt species. The Clays, which are mostly 

 dark blue, and blue black, become red at the to}), 



that there appears to be a transition from the 

 red clay to the argillaceous red limestone, known 

 as the Hunstanton Limestone, or red chalk of 



\\ writers. 



The top beds of the Speeton clay may there- 



ihan the \Y< >< 1 unian of w Inch the 



Upper limit is the Low< * -and of the south 



of England. The other I 1 threefold 



division. So that the Portland and Purbeck lime- 



of Swindon correspond to the Belemnites 



lateralis beds, which ar< sented by the l'p- 



t Russia. The middle beds, 



tly, would spond to the Wealden 



•iod of the south of England, Belgium, and 

 lover, while the >f Belemnites semi-cana- 



liculatus com Is to the Lower Greensand. 



While these beds were being laid down in a 

 region which underwent but little change of level, 

 so that an uninterrupted deposit of clay was ac- 

 cumulated, the land was upheaved, further south, 

 into those shallow water conditions, of which the 

 Portland beds are evidence, which pass without 

 an appreciable break into the lacustrine and ter- 



