230 Geological Society. 



In former communications* Mr .Williamson explained the vertical 

 range of organic remains in the Lias and inferior and great oolites, and 

 in this he showed their distribution in the upper sandstone and shale, 

 the combrash, the Kelloway Rock, and the Oxford Clay. 



The upper sandstones and shales vary considerably in their characters, 

 but they consist of three principal divisions, the highest and lowest 

 being composed of sandstones sometimes ferruginous, and the middle 

 one of clays and shales. The principal localities for the fossils are on 

 the north side of Scalby Beck, near Scarborough, and Burniston Bay. 

 The most characteristic plants are Pecopteris Murrayana, Cyclopteris 

 digitata, and Otopteris obtusa ; but remains of Cycadese and Equiseta 

 also occur. The list of plants is much smaller than that generally 

 given, in consequence of Mr. Williamson having removed, to the great 

 oolite, a bed generally considered as belonging to the upper sand- 

 stones. 



Cornbrash. — This formation seldom exceeds live feet in thickness, 

 and in Cayton Bay consists of the following strata in descending 

 order : 



Fissile oolite 6 inches. 



Softer rock, sometimes ironshot. . 2 feet. 



Hard ironshot rock 2 feet. 



Blue clay, from 3 inches to 4 feet. 



The fossils contained in the fissile upper bed, are chiefly Terebra- 

 tula ovoides, T. obsoleta, Ostrea edulina, and 0. Marshii. The greater 

 portion of the organic remains are found towards the middle of the de- 

 posit, the following being the most abundant : Ammonites Herveyi, 

 Ostrea Marshii, Plagiostoma rigidulum, P. interstinctum, Trigonia 

 clavata, T. costata, Cardium citrinoideum, Unio peregrinus, Amphidesma 

 decurtatum, A. securiforme, My a literata, and Clypeus orbicularis. 

 Twenty other species also occur, but less numerously. In the bed of 

 clay, remains of a small Astacus (?) are obtained, also a shell resem- 

 bling an Unio, and an undescribed Belemnite. Thirteen of the species 

 found in the cornbrash are stated to exist also in the great oolite of 

 Yorkshire, and nine in the coralline or Oxford oolite. 



Kelloway Rock. — This deposit consists of soft sandstones, some- 

 times calcareous, but towards the top it is occasionally very ferrugi- 

 nous ; and it varies in thickness from 35 to 70 feet. The fossils are 

 numerous and highly characteristic, particularly the Ammonites. 

 The ferruginous bed is full of organic remains, consisting chiefly of 

 Belemnites abbreviatus, B. tornatilis, Ammonites Calloviencis, A. sub- 

 Itevis, A. Kbnigi, A. Sutherlandeee, Ostrea Marshii, Gryphea dila- 

 tata, /3. The most abundant species in the sandstones are, Ammo- 

 nites jlexicostatus , A. subleevis, A. gemmatus, A. Calloviencis, A. per- 

 armatus, A. ichthyodorsus (W.), A. gamma (W.), A. rotifer (W.), 

 A. oblisus (W.), Belemnites abbreviatus, B. tornatilis. Turbo sulcosto- 

 mus, Terebratula ornithocephala, T. socialis, Gryphaa dilatata, Ostrea 

 Marshii, Avicula Braamburiensis , A. expansa, Lucina lyrata, Amphi- 

 desma recurvum : 1 8 other species of testacea occur, though less abun- 



* Proceedings, vol. ii., pp. 82, 429 ; or Lond. and Edinb. Phil. Mag. 

 vol. v. p. 222., vol. X. p. 137. J Geol. Trans. Sec. Ser. vol. v. Part I., p. 223, 

 et teq. 



