62 



thinned down to less than 20 feet^ and is there represented by 

 the Parhinsoni beds, the middle and lower divisions being absent. 

 In one or two sections in the Northern Cotteswolds the 

 following beds belonging to this zone may be distinguished: — 



FxTLLEES-EAETH WITH Ostrea acv/miuata. 



A. — Upper Trigonia Grit. — Consisting of thin-bedded brown 

 Oolitic Ragstones, containing many fossils, chiefly as moulds. 

 The following are the most characteristic: — Trigonia costata, 

 T. formosa, T. signata, BhyncJwnella spinosa, Terebratula glohata, 

 Ammonites Parhinsoni, A. Martinsii, Clypeus Plotii. 



B. — GrypMte Grit. — Almost entirely composed of the valves 

 of Gryphcea sublohata, imbedded in a fine hard calcareo-siliceous 

 matrix. It is an oyster-bed of greater or less thickness, and is 

 exposed in many sections in the Northern Cotteswolds; it is 

 absent south of Rodborough Hill. Besides Gryphoece, it contains 

 many species of Mollusca. 



C. — Lower Trigonia-grit. — Light coloured, or brownish. Oolitic 

 Ragstone, often iron- shot; containing, in some places, numerous 

 fossils in fine preservation. Echinobrissus clunicularis, Pedina 

 rotata, Holectypus depressus, Lima gihhosa, Tancredia donaciformis, 

 Gervillia Hartmanni, and Perna rugosa, appear first in this bed. 



D. — Chemnitzia-grit. — Consists of a hard bed of Ragstone 

 above, and bands of Marls and Clays below. The Marls contain 

 Chemnitzia procera, Fishes' teeth, and Crustacean remains. The 

 Marls rest upon a thick bedded Oolitic Limestone, often bored 

 by Annelida. 



The Upper division of the Inferior Oolite has been much 

 denuded from Cleeve Hill, and there is now but a feeble 

 representation of the beds of this group in that locahty. Those 

 that remain remind me of the section of the same at Ravensgate 

 Hill, both as regards the lithological character of the rocks, and 

 the suite of fossils they contain. This zone is seen in a small 

 exposure which faces the east, and overlooks the valley leading 

 to Postlip Mills. The strata are composed of beds of brown 

 rubbly iron-shot Oolite, from five to six feet in thickness. This 



