200 



bluish marls and shales, or bands of clay in yellow siliceous 

 sands, containing large spherical blocks of sandy Limestone : a 

 capital section through the Forest marble and Great Oolite at 

 Crickley-Barrow, shows the lithological characters of these two 

 formations : — 



Forest Marble. 



Great Oolite. 



Shelly Oolite formed of 

 organic debris, obliquely 

 laminated in different 

 directions. 



Hard, white, sandy Lime- 

 stone, thickly and regu- 

 larly bedded. 



Small oysters, Pec- 

 tens, &c., in great 

 profusion on the 

 slabs. 



Not very fossiUferous. 



Terebratula maxil- 



lata, numerous. 



The organic remains in the Forest marble are abundant in 

 individuals, but not numerous in species, and in this respect 

 the formation presents a striking difference to the Hampton 

 freestones ; many of them are specifically identical with those 

 of the Great Oolite, there being only a small minority which 

 are not found in the basement beds of the Minchinhampton 

 quarries. 



Cornhrash. — Is a coarse thin-bedded Limestone, having bands 

 of brown and grey marls alternating, and interstratified 

 therewith. Near Chippenham, Wilts, it is well exposed 

 and very fossiliferous, containing numerous Brachiopoda and 

 Anatinidce. I have collected all the fossils in the subjoined 

 list from the Wiltshire Cornbrash : — 



CONCHIFEEA. 



Gresslya peregrina, Phil. 

 Myacites securiformis, Phil. 

 Homomya gibbosa, Bow. 

 Myacites calceiformis, Phil. 

 Ceromya concentrica. Sow. 

 Pholadomya Heraulti, Ag. 

 Lima duplicata. Sow. 



n cardiiformis, Sow. 



II pectenifonnis, Schloth. 

 Modiola Sowerbii, d'Orh. 



Avicula echinata, Soiu. 

 Trigonia costata. Sow. 

 Astarte excavata, Soiv. 

 Goniomya litterata, Phil, 

 GerviUia crassicosta, Mor. and Lye. 

 Modiola bipartita, Soiu. 

 Avicula costata, Sow. 

 Pecten lens, Soiv. 



•I vagans. Sow. 



II rigidus, Soiu. 



Bkachiopoda. 



Terebratula intermedia. Sow. Terebratula obovata. Sow. 



maxillata. Sow. Rhynchonella concinna, Sow. 



