A MONOGRAPH 



OF 



BRITISH OOLITIC AND LIASIC BRACHIOPODA. 



PRELIMINARY REMARKS. 



Under the lowest member of the cretaceous system, we discover an extensive series of 

 strata, consisting of different kinds of sands, sandstones, limestones, and clays, divided into 

 a number of groups, known to geologists under the name of Jurassic, or Oolite and Lias 

 Rocks. These form together a system of great thickness, traversing our island from the 

 Yorkshire Coast to that of Dorsetshire in the shape of a band, varying in breadth from a 

 few miles to between fifty and sixty in its midland course. 



Great Britain is considered the typical country whence continental geologists obtained 

 the first clue to those divisions which, with differences only in the nature of their com- 

 position, have been traced over many parts of our globe. 



The object of the present Monograph is not to enter into the Geology of this system, 

 which has been so ably illustrated by many celebrated British and Continental Geologists, 

 but an endeavour to trace the forms or species of Brachiopoda which lived at different 

 periods, while this vast amount of sediment was being deposited in the depths of the sea. 



It may, however, be useful for the sake of reference, to give a tabular view of the 

 different members of the Oolite and Lias series. We cannot do better than extract it from 

 Mr. Tennant's ' Stratigraphical List of British Fossils :' 



Potland Stone and Sand 



Kimmeridge Clay 



Isle of Portland ; Brill, &c., 

 Aylesbury, Bucks ; Thame, 

 Oxon ; Tisbury, Wilts. 



Coarse oolitic shelly limestone; sometimes fine-' 

 grained or compact, thick-bedded, and with 

 layers of chert, and with subordinate beds of 

 sand. 



"N Kimmeridge, Dorsetshire ; 

 Dark blue and grayish laminated clay, with gyp- f near Oxford ; Stone and 

 sum and bituminous shale. V Hartwell, Bucks ; 



J Swindon. 



B 



near 



