GEOLOGY OF THE BRISTOL COAL-FIELD. 325 



17.— [1526]. — Aranea led, or grey limestone, full of the 

 Lithostrotion aranea. The delicate web -like tracery of the septa are 

 shewn very distinctly. It contains a small branched coral whose 

 name has not been definitely determined, 



Lithostrotion aranea (Edwds.), irregulare (Edwds.),' junceum 

 (Edwds.) ; Producta punctata (Mart.). 



"We now come to the Great Quarry, another extensive section, 

 1185 feet long, and the same height as the Black Kock. Here the 

 limestone is generally lighter in colour, and, in some places, very 

 bituminous. Between the limestone beds we frequently find cubic 

 crystals of the Fluor Spar. At the western end is a veiy singulaij 

 fracture of the beds by subsidence. During the progress of 

 deposition, a portion has evidently been washed away, letting the 

 superincumbent roof of five or six beds fall in ; this was evidently 

 not a recent occurrence, because the subsequent thickness of some 

 200 feet was afterwards regular, and shows no sign of disturbance. 



18.— [1539]. — Longispinosus led occurs about 15 feet before the 

 commencement of the Great Quarry. It is a smooth, thin, and 

 argillaceous bed completely covered with Trilobites, a Productus 

 with very long spines, Bryozoa, and other organisms. 



Producta longispinosa (Sow,) ; Phillipsia pustulata (Schloth.) ; 

 Ceriopora rhomlifera (Goldf.) Lithostrotion junceum (Edw.) ; 

 JEntomostraca ; Foraminifera. 



19. — [1552]. — JEiiomphalus led is one of the first beds of solid 

 limestone with which we meet in the quarry. It is a rather light 

 coloured limestone, and very fossiliferous, and contains some good 

 specimens of Eaomphalus and Producta. 



Euomphalus nodosus (Sow.), calyx (PhilL); Producta Martini 

 (Sow.), Co'r« (D'Orb.); Rhynchonella acuminata {^ow.). 



20. — [1617]. — I'ortlochi led is fall of the beautiful astreiform 

 corals in brown limestone, a section cut from any part is an equally 

 good example. 



Lithostrotion PortlocTci (Edwds.) ; Cyathophyllum regium (PhilL), 

 turlinatum (So*v.); Michehnia tenuisepta (Goldf.). 



