816 STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
TABLE OF THE BRITISH CRETACEOUS SYSTEM—continued. 


English Stratigraphical Subdivisions. 3 Palxontological Zones (Marine). 


LowER CRETACEOUS. 
Southern Type. | Northern Type. 
(Fluviatile, and in (Marine.) 
upper part marine.) 
S | Sands, clays, | Upper _ Neoco- Upper. Perna Mulletti, Exogyra sinu- 
# & | limestones,&c.,| mian, upper] . ata, &e. 
E22 in Kent, Sur-| 150 feet of | © 
8 | rey, Sussex,} Speeton Clay, | * 
ws \ Hampshire. Yorkshire. 
Weald Clay. Middle Neoco- | #| Middle. Zone of Pecten cinetus, Ancy- 
mian, next} © loceras beds, 
150 feet of | ° 
| Speeton Clay, | ° 
cS and “Tealby | ° 
rs beds.” Zz 
| Hastings sands | Lower Neoco- Lower. Zone of Ammonites speeton- 
and clays,pass- | mian, next ensis. 
ing down into; 200 feet of i A. noricus. 
Purbeck beds. | Speeton Clay. | 33 A. astierianus, 
LowrEr CRETACEOUS oR Neocomran.'—Between the top of the Jurassic 
system and the strata known as the Gault, there occurs an important 
series of deposits to which, from their great.development in the neigh- 
bourhood of Neufchatel (Neocomum) in Switzerland, the name of 
Neocomian has been given. ‘This series, as already remarked, is repre- 
sented in England by two distinct types of strata. In the southern 
counties, from the Isle of Purbeck to the coast of Kent, there occurs a 
vast succession of estuarine and fluviatile sands and clays termed the 
Wealden series. ‘These strata pass up into a minor marine group known 
as the Lower Greensand, in which some of the characteristic fossils of 
the Upper Neocomian rocks occur. ‘The Wealden beds therefore form a 
fluviatile equivalent of nearly the whole of the continental Neocomian ~ 
formations, while the Lower Greensand represents the later marginal 
deposits of the Neocomian sea, which gradually usurped the place of the 
Wealden estuary. The second type, seen in the tract of country extend- 
ing from Lincolnshire into Yorkshire, contains the deposits of deeper 
water forming the westward extension of an important series of marine 
formations which stretch for a long way into central Europe. 
Neocomian.—The marine Neocomian strata of England are well 
exposed on the cliffs of the Yorkshire coast at Filey, where they occur in 
a deposit long known as the “Speeton Clay.” ‘his deposit has been 
shown by Mr. Judd to belong partly to the Jurassic and partly to the 
Neocomian series. ‘I'he Neocomian portion is divided by him into three 
formations, as follows :—1. Lower Neocomian (200 feet or more), con- 
taining in ascending order the zones of (a) Ammonites astiertanus, (b) Am. 
noricus, (c) Am. spectonensis. Among its fossils are Toaster complanatus, 
Ancyloceras puzosianum, A, Duvalii, A. Emericti. 2. Middle Neocomian 
(150 feet), composed of (a) Ancyloceras beds, (b) Zone of Pecten cinctus, 
? Consult on marine type Judd, Q. J. Geol. Soc. xxix. 218; xxvi. 326; xxvii. 207; 
Geol. Mag. vii. 220; Geology of Rutland, in Mem. Geol. Surv. ; Meyer, Q. J. Geol. Soe. 
Xxvili. 243; xxix. 70. 

