38 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 6, 



and at Burford, on the Upper Lias. This zone is the most per- 

 sistent of the three subdivisions of the Inferior Oolite, and is the 

 only representative of that formation in the south-eastern parts of 

 the county of Gloucester ; for, whereas at Leckhampton Hill the 

 three zones of that formation attain a thickness of 264 feet, at Bur- 

 ford, a distance eastwards of twenty miles, the Inferior Oolite is 

 reduced to less than 20 feet, and is there represented by the Par- 

 kinsoni-zone, — the middle and lower zones being altogether absent. 

 In the Northern Cotteswolds, in one or two sections, the following 

 beds may be distinguished. 



Fuller' s-earth with Ostrea acuminata. 



A. Upper Trigonia-grit. — Consists of thin-bedded, brown, oolitic 



ragstones, containing many fossils, chiefly in the form of 

 mordds. Trigonia costata, T. formosa, T. signata, Rhynchonella 

 spinosa, Ammonites Parkinsoni, A. Martinsii. 



B. Gryphite-grit. — Almost entirely composed of the valves of 



Gryphcea sublobata, imbedded in a sandy or calcareous ma- 

 trix. It is an oyster-bank of greater or less thickness, and 

 is exposed in many sections in the Northern Cotteswolds, 

 but is absent south of Bodborough Hill. 



C. Lower Trigonia-grit. — A light-coloured, grey or brown, thin- 



bedded, sandy, oolitic or argillaceous ragstone. It contains 

 in many places a great abundance of fossils. Clypeus Plotii, 

 Echinobrissus clunicularis,Holectypus depressus,Pedina rotata, 

 Terebratula globata, and Lima gibbosa appear for the first 

 time in this bed. 



D. Chemnitzia-grit. — This consists of a hard crystalline bed of 



ragstone above ; with bands of marls and clays below. The 

 marls contain Chemnitzia procera, fishes' [teeth and palates, 

 with remains of Crustacea. 

 Thick-bedded oolitic limestone {freestone) often bored by Annelida. 



This division of the zone of Ammonites Parkinsoni, in the works 

 of Murchison, Hull, and Lycett, differs in some important particulars 

 from the description of the same beds given by former authors. The 

 " Clypeus-grit," with Terebratula globata, is represented as the 

 uppermost stage of the Inferior Oolite, overlying the Upper Tri- 

 gonia-grit ; but I shall endeavour to demonstrate, by the sections to 

 be described in the sequel, that Clypeus Plotii and Terebratula glo- 

 bata swarmed in the ocean with Trigoniai long before the Gryphite- 

 grit was deposited ; although this sea-urchin and its congeneric 

 Echinidai lived in the waters which deposited the Fuller's-earth, 

 Great Oolite, and Cornbrash, where all these species became extinct. 

 In fact, the fauna of the Lower Trigonia-grit presents a remarkable 

 contrast to that of the freestones on which it rests, both in genera 

 and species. The floor of the sea, formed by the freestones, was 

 indurated; and the solid rock was perforated by the Annelida which 

 lived in the Trigonia-stage. Many species likewise of Fish, Ammo- 

 nites, ConcJiifera,Bracliiopoda, Echinodermata, and Corals now appear 



