Subdivisions of the Inferior Oolite in the South of Enyland. 377 



Pea-grit loses its pisolitic character ; and in the eastern part of the 

 hill-district the Freestones thin out and finally disappear; the In- 

 ferior Oolite being represented at Stow-on-the-Wold and at Bur- 

 ford by the zone of Ammonites Parkinsoni, with its light-coloured 

 ragstones, filled with an abundance of Clypeus Plotii, Klein, and 

 forming a " Clypeus- grit." 



The fossils of the Pea-grit and Freestone, and of the Oolite-marl or 

 Fimbria-bed, were then enumerated. The Oolite-marl was described 

 as having been probably derived from the debris of a Coral-reef: its 

 Nerinsean limestone was particularly alluded to. 



The section at the Peak near Robinhood's Bay afl^orded the author 

 the equivalents of the zones of Am. Humphriesianus and Am. Mur- 

 chisoneE, and was described in full. 



The zone of Am. Humphriesianus was next treated of. Its syn- 

 onyms are " Inferior Oolite of Dundry Hill," Conybeare and 

 Phillips ; " Grey limestone, Bath or Great Oolite " (Yorkshire), 

 Phillips ; " Eisenrogenstein (part) und Walk-Erde Gruppe," From- 

 herz ; " Brauner Jura y und h," Quenstedt ; " Calcaire ferrugineux," 

 Terquem ; " Blaue Kalke. Korallenschicht, Giganteus-Thone, und 

 Ostreen-Kalke " (Quenstedt), Pfizenmayer. The best types of this 

 zone, so well characterized by peculiar Gasteropods and Cephalopods 

 and its ferruginous oolitic grains, are seen in the section at Dundry 

 Hill, at Yeovil and Sherbourne in Somerset, and at Burton-Brad- 

 stock and Chideock in Dorset. Just as the thinning-out of the 

 Murchisonae-zone and the absence of the Humphriesianus-zone near 

 Burford and other localities in the N.E. parts of the Northleach di- 

 strict brings the Parkinsoni-zone nearly into juxtaposition with the 

 clays of the Upper Lias, so the thinning-out of the Murchisonae- zone 

 at Dundry Hill brings the zone of Am. Humphriesianus into close re- 

 lation with the " Sands of the Upper Lias," and has caused it to be 

 mistaken for the "Cephalopoda-bed" of Frocester and Leckhampton 

 Hills. In the Northern Cotteswolds the Humphriesianus-zone is but 

 feebly represented. 



The Dundry Hill section was then described in a note by Mr. R, 

 Etheridge, F.G.S., as comprising — 1st (lowest), Lower Lias; 2nd, 

 perhaps the " Lias Sands ;" 3rd, the Shell-bed ; 4th, Ammonite-bed 

 (not equivalent to the "Cephalopoda-bed" of the Cotteswolds); 

 5th to 9th, shelly beds, ragstone, fine-grained oolite, and freestone ; 

 some of the latter representing the Parkinsoni-zone. 



Dr. Wright then described the section in Gristhorpe Ba)s from 

 the Cornbrash to the Millcj)ore-bed ; — equal to the zone of Am. 

 Humphriesianus. The fossils of these marine and freshwater beds 

 were noted as existing in the cabinets of Leckenby, Bean, and others. 



The zone of Am. Farhinsoni has the following synonyms, accord- 

 ing to the author: — " Trigonia-grit and Gryphite-grit," Murchison 

 and Strickland ; " Ragstone and Clypeus-grit," Hull ; " Spinosa- 

 stage," Lycett ; "Brauner Jura e" (pars), Quenstedt; " Parkin- 

 sonthone, Brauner Jura o und e " (pars), Pfizenmayer; " Calcaire h 

 Polypiers," Terquem ; " Die Schichten des Ammonites Parkinsoni," 

 Oj)pel. This zone is the most persistent of the three subdivisions 



Phil. Mac,. S. 4. Vol. 17. No. 115. Mat/ 1859. 2 C 



