482 
THE GEOLOGIST. 
LOWER OOLITES. LIAS. 
Cornbrash. Upper Lias clay. 
Forest-marble. Marlstone. 
Bath Oolite. Lower Lias. 
Northampton sand. 
I cannot dwell on the lithology of these beds, which differ not in 
mineral composition from equivalent strata in other parts of England ; 
but, before describing their fossil contents, I will content myself by 
just tracing the boundaries of the various divisions as I go on. 
The Upper Oolites — viz., the Portland rock and Kimmeridge clay- 
are greatly developed in the Yale of Aylesbury ; that fertile tract of 
country lying between the Cretaceous ridge known as the East 
Anglian heights and the Oolitic hills of Oxfordshire. Hartwell and 
Stone (about two miles from the town of Aylesbury) are equally 
renowned for the beauty of their organic remains. The first fori 
Kimmeridge clay, and the second for Portland rock fossils. As the 
clay and limestone are very useful for economic purposes, several pits 
and quarries are found in the neighbourhood. The Portland rock is 
capped by a thin layer of Purbeck stone with a subordinate band of 
carbonaceous earth, which represents the dii't-bed of the Isle of i 
Portland. In the limestone, remains of coleopterous insects were 
found by the Rev. P. B. Brodie ; with the exception of these fossils, 
which are now rarely met with, scarcely any others are found. The 
Portland rock, however, has organic remains in great abundance, but 
not of great variety : the following list will show the most common 
of them : — 
Area. 
Ammonites biplex. Sow. Panopsea. 
{var. rotundus) Lucina Portlaudica, Sow. 
Pleurotomaria. Pecten lamellosus, Soio. 
Natica elegans, Soio. Lima rustica, Soio. 
Cardium dissimile, Sow. Myacites recurva, Fhil. 
Trigonia gibbosa. Sow. Ostrsea expansa, Sow. 
Fossil wood, &c. 
incurva, Sow. 
The Portland rock extends some way further north than Stone, 
and finally disappears near Bletchley. The clay at Hartwell is of a 
dull leaden colour, and is very fossiliferous indeed. But the bitu- 
minous shales which occur in this formation in Dorsetshire have not 
been noticed here, though lignite is pretty abundant. The following 
is a list of fossils from the Kimmeridge clay of Bucks : — 
Ichthyosaurus \ Ammonites biplex, Sow. 
Plesiosaurus ( Bones, Belemnites Owenii, Fratt. 
Cetiosaurus J &c. Pleurotomaria reticulata, Sow. 
Pliosaurus * Pholadomya sequalis. Sow. 
Myacites recurva, Phil. 
