A. J. Jukes-Browne — On the term Neocomian. 317 



feel justified in subjecting them to some slight criticism. First, 

 therefore, as to the grouping of the zones ; there does not seem any 

 very good reason why the zone of Ammonites speetonensis should be 

 classed with the lower zones rather than with the middle group. 

 Prof. Judd identified twenty-six species from this zone, and of these 

 only eight occur in the zone of Am. noricus, while thirteen species 

 (50 per cent.) range up into the Pecten cinctus beds : again in Lincoln- 

 shire the only determinable Ammonites obtained from the clays 

 overlying the Tealby ironstones with Pecten cinctus were the varieties 

 of Am. speetonensis (concinnus and venustus). I am inclined, there- 

 fore, to think that a part at any rate of Prof. Judd's speetonensis zone 

 should be grouped with his Middle division rather than with the 

 Lower. The noricus zone does not appear to have any equivalent 

 in Lincolnshire, and it is quite possible that the masses of clay 

 which form the noricus and speetonensis zones in Yorkshire did not 

 extend into Lincolnshire, no contemporaneous deposits being formed 

 in the latter area. 



In the next place it does not appear to me so very clear that the 

 fauna of the Upper division has a closer analogy with that of the 

 Atherfield Clay than that of the Middle division has. There is no 

 very marked correspondence between any part of the northern and 

 southern series, the areas in which they were deposited were evi- 

 dently to a great extent separated from one another, many species 

 common in the one area do not occur in the other, and the time 

 range of some of those species which do occur in both series appears 

 to be different, thus Perna Mulleti is abundant in the Atherfield Clay 

 of the south, while in Yorkshire it is only quoted from the Upper 

 division. It occurs, however, in the middle clays of Donington in 

 Lincolnshire, and it is these clays both in Yorkshire that I am 

 inclined to regard as the homotaxial equivalents of the Atherfield 

 Beds, the abundance of Ifeyeria (though the species are different) 

 and of Exogyra sinuata are features in common. 



If these views be accepted, the Yorkshire and Lincolnshire series 

 can be brought into greater harmony, and both may be correlated 

 with the southern type as follows : — 



Yorkshire. Lincolnshire. Isle of Wight. 



,,„, - ( Clays without fossils Carstone ? ) «, , ,. „ ■■ 



150feet { Cement beds absent? } Shankhn Sands. 



/ Pecten cinctus beds ) Donington Clay ( "Walpen Sands, etc. 



250 feet I Ancyloceras beds j and Tealby Beds \ Atherfield Clay. 



( Speetonensis zone ) Wanting i ^ art °^ *^ e ^ ea ^ en 



lOOfppf I Zone of Am. noricus { ° ' .' ' \ Beds. 



\ Zone of Am. Astierianus Spilsby Sands 



Unconformity — Hastings Sands. 



This view finds support in the opinion expressed by M. Coquand, 1 

 that the only part of the Speeton Clay series which can be correlated 

 with the Neocomien of the south of France is the zone of Am. astieri- 

 anus, and that all above it must be referred to the Urgonien and 

 Aptien divisions. The zone of Am. astierianus is acknowledged by 



1 Bull. Soc. Geol. de France, 2nd ser. vol. 26, p. 211. 



