298 JURASSIC. 



bedding, and generally of a yellowish-white colour.^ Layers of 

 sandy marl occasionally form partings between the beds of stone. 

 The Great Oolite is rich in univalve Mollusca, such as Alaria, 

 Cylindritcs, NerincBa Volizii, Nerita, Patella ciiigulata, P. riigosa, 

 Chamiitzia, Cerithitim qiiadricinctum, Natica, Trochotorna ohhisa, Purpu- 

 roidea Morrisii, Pteroceras Wright ii; amongst the bivalves are Cardium 

 Stricklandi, Macrodoti Hirso7ie7isis, Ceroinya, Cypricardia, Gervillia, 

 Tn'gojiia imhricata, T. Moretoni, Pholadomya, Tancrcdia brtvis, Astarte 

 ex cava ta, Area, Ostrea gregaria, Pee ten lens, P. vagans, Lima eardii- 

 formis, L. duplieata, Modiola imbrieata, Pachyrisma grande, and Opis 

 hinnlatiis. Cephalopoda are not abundant; they include Aynmonites 

 siibcojitraetiis. Nautilus, and Bele7miites. Among the Brachiopoda 

 are Rhynchonella eojicinna, Tercbrattda perovalis, T. maxillata, 

 Waldheimia digona, etc.^ The Coral Calamophyllia [Euno??iia) 

 radiata, is common near Bath ; other species occur at various 

 horizons, including Isastreca, Cofivexastrepa, Thavuiastrcca, etc., and 

 the ' Button-stone,' Anabacia orbulites? Among Echinodermata are 

 Hemicidaris, Acrosalenia hemicidaroides, etc., of which many spines 

 and plates are found, also Millericrinus Pratli. Diastopora ven- 

 iricosus is not uncommon. Fragments of Crustacea {Glyphea) are 

 sometimes met with. Of Fishes, we find the large quadrangular 

 palatal teeth of Strophodus, spines and teeth of Hybodus, and the 

 small spherical teeth of Lepidotics (sometimes termed ' Fishes' 

 eyes'). Teeth and bones of Saurians {Cetcosaurus, etc.) are 

 occasionally met with. Some Reptilian eggs found in the Great 

 Oolite at Hare-bushes quarry, near Cirencester, were described by 

 Prof. Buckman, who named them Oolithes BalhoniccE} Fragments 

 of lignite occur in places. In many localities the Great Oolite 

 appears destitute of fossils, or the organic remains are so broken 

 up that not a single perfect specimen can be obtained. 



The thickness of the Great Oolite varies from 50 to 150 feet. 



The Great Oolite in the neighbourhood of Bath was thus 

 divided by Lonsdale:'' — 



Feet 

 (\. Coarse, shelly limestones \ 



Upper Rags. < 2. Tolerably fine oolites (Scallet) > 20 to 55 



(3. Tough, brown, argillaceous limestone ) 



Fine freestones (Weatherstone, etc.) lO to 30 



Lower Rags, Coarse, shelly limestones 10 to 40 



Beds of Coral and shell-beds with small Gasteropods occur in 

 the upper beds at Farley Down, at Murrel (Murhill) near Winsley, 

 and Ancliff (Avoncliff) near Bradford-on-Avon, as noted by Mr. 



1 The formation was termed the Great Oolite of Bath, or Upper Oolite, by 

 William Smith, in 1S15. 



2 See J. Lycett, The Cotteswold Hills, J. Phillips, Geol. Oxford, etc. In the 

 Oxford area we owe our knowledge of the fossils of the Great Oolite Series largely 

 to collections made by Mr. J. Whiteaves, Rep. Brit. Assoc, i860. Sections, p. 104. 



^ R. F. Tomes, Q.J. xxxix. 170; xli. 170. 



* Q.J. xvi. 107, xiv. 117; W. Carruthers, Q. J. xxvii. 447. 



^ T. G. S. (2), iii. 250, 254. 



