792 STRATIGRAPHICAL GEOLOGY. [Boox VI. 
the formations between the Upper Lias Clay and the top of the Great — 
Oolite consist of sands with beds of ironstone, known as the Northampton 
Sand. The higher portions of the sandy series contain estuarine shells 
(Cyrena) and remains of terrestrial plants. ‘hese strata swell out into 
a great thickness in Yorkshire, where they form the lower series of 
sandstones, shales, and coals. A tolerably abundant fossil flora has been 
obtained from these Yorkshire beds. With the exception of a few 
littoral fucoids all the plants are of terrestrial forms. They comprise 
about 60 species of ferns, among which the genera Pecopteris, Sphenopteris, 
Phlebopteris, and Teniopteris are characteristic. Next in abundance come 
the cycads, of which more than 20 species are known (Otozamites, Zamites, 
Pterophyllum, Cycadites). Coniferous remains are not infrequent in the 
form of stems or fragments of wood, as well as in occasional twigs with 
attached leaves (Araucarites, Brachyphyllum, Thuyites, Peuce, Walchia, 
Cryptomerites, Tamites). 
The Fuller’s Earth is an argillaceous deposit which in the neigh- 
bourhood of Bath attains a maximum depth of nearly 150 feet, but dies 
out in Oxfordshire and is absent in the eastern and north-eastern 
counties. Among its more abundant fossils are Goniomya angulifera, 
Ostrea acuminata, Rhynchonella concinna, R. varians ; but most of its fossils 
occur also in the Inferior Oolite. 
The Great Oolite consists, in Gloucestershire and Oxfordshire, of 
three groups of strata: (a) lower group of thin-bedded limestones with 
sands, known as the Stonesfield Slate ; (b) middle group of shelly and 
yellow or cream-coloured, often oolitic limestones, with partings of marl 
or clay—the Great Oolite; (¢) upper group of clays and shelly lime- 
stones, including the Bradford Clay, Forest Marble, and Cornbrash. 
These subdivisions, however, cease to be recognizable as the beds are — 
traced eastward. The Bradford Clay of the upper group soon dis- 
appears, and the Forest Marble, so thick in Dorsetshire, thins away in 
the north and east of Oxfordshire, the horizon of the group being perhaps 
represented in Lincolnshire by the “‘ Great Oolite Clays” of that district. 
The Cornbrash, however, is remarkably persistent, retaining on the 
whole its lithological and paleontological characters from the south- 
west of England nearly as far as the Humber. The limestones of the 
middle group are less persistent, though they can be recognized as far 
as the middle of Lincolnshire. The lower group, including the Stones- 
field Slate, passes into the upper part of the Northampton Sand and the 
‘“‘Upper Estuarian series.” (See Mr. Judd’s Geology of Rutland.) 
The fossils of the Stonesfield Slate are varied and of high geological 
interest. Among them are about a dozen species of ferns, the genera 
Pecopteris, Sphenopteris, and Teeniopteris being still the prevalent forms. 
The cycads are chiefly species of Palozamia, and the conifers of Thuyites. 
With these drifted fragments of a terrestrial vegetation there occur 
remains of beetles, dragon-flies, and other insects which had been blown 
or washed off the land. The waters were tenanted by a few brachiopods 
(Rhynchonella and Terebratula ), by lamellibranchs (Gervillia, Lima, Ostrea, 
Pecten, Astarte, Modiola, Trigonia, &c.), by gasteropods (Natica, Nerita, 
Patella, Trochus, &c.), by a few ammonites and belemnites, and by placoid 
and ganoid fishes, of which about 50 species are known. The reptiles 
comprise representatives of turtles, with species of Ichthyosaurus and 
Plesiosaurus, Ceteosaurus, Teleosaurus, Megalosaurus, and Lthamphorhynchus. 
