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THE GEOLOGIST. 



LOWER OOLITES. LIAS. 



Cornbrash. Upper Lias clay. 



Forest-marble. Marl stone. 



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 for 

 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 dirt-bed of the Isle of 

 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 Portlandica, Sow. 



Pleurotomaria. Pecten lamellosus, Sow. 



Natica elegans, Sow. Lima rustica, Sow. 



Cardium dissimile, Sow. Myacites recurva, Phil. 



Trigonia gibbosa, Sow. Ostrjea expansa, Sov). 



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, Pratt. 



Cetiosaurus C &c. Pleurotomaria reticulata, Sow. 



Pliosaurus ) Pholadoniya seqnalis, Sow. 



Myacites recurva, Phil, 



