10 



BRITISH FOSSIL CORALS 



reef on the opposite side of the valley, the whole of the intervening space having been 

 excavated by denudation. The coral-bed consists of large masses of coralline limestone 

 imbedded in a fine-grained cream-coloured mudstone. The corals are in a highly 

 crystalline state, so that the genera and species are determined with difficulty. The bed 

 is from fifteen to twenty feet in thickness, and forms one of the finest examples of fossil 

 coral-reefs that Dr. "Wright is acquainted with in the district. The bed may be traced 

 along the escarpment, in a north-westerly direction, for several miles, to Witcomb and 

 Crickley on the west, and to near Cubberley and Cowley on the east, where it Avas worked 

 several years ago. Judging from the thickness of the bed, and the abundance of corals 

 it contains, it must have formed a barrier-reef of considerable magnitude in the Jurassic 

 sea. The following is a section showing the relative position of the Lower Coral-reef. 



Section of the Loicer Coral-reef, in the Inferior Oolite, at the Quarry, North Frith Wood, 



near Broicn's Hill, Gloucestershire. 



Lithological Characters and 

 Thickness. 



Beds 



Cream-coloured Marl, with 

 several inconstant layers of 

 Mudstone, upper part pass- 

 ing into a loose, friable 

 Freestone, with large Tere- 

 bratula fimbria. 

 From' 20 to 25 feet. 



Fine-grained oolitic Limestone, 

 very white, and emitting a 

 metallic ring when struck 

 with a hammer. 

 40 to 50 feet. 



Coarse brown ferruginous 

 Oolite. 



Masses of Coralline Limestone, 

 imbedded in a light-coloured 

 Mudstone; the Corals highly 

 crystalline, forming the chief 

 part of the bed. 

 15 to 25 feet. 



Brown ferruginous pisolitic 

 rock. Pea-grit structure not 

 much exposed. 



Upper Freestones. 



Oolite-marl. 

 Middle Coral-bed. 



Freestones. 



Lower Ragstones. 



Lower Coral-reef. 



Pea-grit. 



Organic Remains. 

 Fossils. 



Leading 



Thamnastrcea, Isastrcea, Axo- 

 smilia, Terebratula fimbria, 

 T. carinata, T. maxillata, 

 RhynchonellaLycetti,Lucina 

 Wrighti, Lima pontonis. 



Shelly fragments, not determin- 

 able. 



Terebratula plicata. 



Latimceandra, Thamnastrcea, 

 Isastrcea, Axosmilia, The- 

 cosmilia, Pecten Dewalquei, 

 Trichites, Lueina TVrighti. 



Lima sulcata, Hinnites abjectus, 

 Ceromya Bajociana, Avicula 

 complicata, Nerita costata, 

 Trochotoma carinata, Py- 

 gaster, Hyboclypus, Dia- 

 dema. 



