222 Geological Society. 



a variety of G. cymbium ? together with Lima proboscidea, Pholado- 

 mya ambigua and P. Jidiada, Trigonia striata, &c. &:c. 



(2.) Great Oolite — consisting of upper and lower rags, inclosing a 

 fine-grained building-stone, the united thickness of which in the pre- 

 cipitous escarpment of Leckhampton is estimated at upwards of 120 

 feet. The fossils are nearly the same as those of the great oolite of 

 Bath. The Bradford clay and Fuller's earth are entirely absent, the 

 upper rags of the great oolite being separated from the forest mar- 

 ble by only a small loamy wayboard of a few inches, and the lower 

 rags pixss into the inferior oolite. 



(3.) The Inferior Oolite is described at its maximum thickness in 

 Crickley Hill, occupying about 00 feet, whence it thins off in its 

 range to the north-east, presenting about half that thickness beneath 

 Cleeve Clouds. In this district the formation assumes a remarkable 

 mineral aspect ; for, although it contains some subordinate beds of 

 oolitic structure, it is in general made up of coarse concretions, 

 which, being flattened, give to it the appearance of a nummulite rock. 

 Numerous coralline bodies are described as being spread over the 

 sandy, ferruginous faces of the stronger beds, .'^mong the fossils 

 there are many species common to other formations of the oolitic 

 series. 



(4.) The Lias formation having usually a cap of marlstone, the 

 upper lias shale of Yorkshire being wanting, is observed to rise to 

 heights ranging from 300 to 500 feet above the Vale of Gloucester, 

 beneath which it has been penetrated at Cheltenham to the depth of 

 230 feet ; so that the greatest thickness of the formation is estimated 

 at about 700 feet. 



The marlstone is best seen in the insulated hills of Robinswood 

 and Church Down, in the first of which the principal stratum is a 

 thick-bedded, calcareous grit, separated from a covering of sandy and 

 ferruginous, inferior oolite by thin courses of marl and marlstone. 



On Church Down, of which it constitutes the summit, the marl- 

 stone is quarried to the depth of 16 or 20 feet, in beds of hard, blue 

 and grey calc-grit, abounding in Gryphcca gigaidea and Belemnites 

 pencillatus. In the Cotteswolds, this subformation has been de- 

 tected by the author in the form of only a finely laminated, micaceous 

 sandstone, alternating with marls, on which the springs generally 

 burst forth after percolating through the strata of the inferior oolite 

 — thus giving rise to the Chelt and other tributaries of the Severn, 

 as well as to the Isis or Thames. 



The upper beds of the lias, beneath the marlstone, are best exposed 

 near the culminating part of the new London and Cheltenham road, 

 which traverses the Cotteswolds at their lowest point, viz., about 

 500 feet above the sea, and where a great denudation of the over- 

 lying oolites has taken place. Here, these beds are rich in fossils, 

 including Ammonites Walcottii, A. undulatus, Nucula (nov. spec), 

 Jnoceramus dubius, Belemnites acutus, B. tubularis, and B. pencilla- 

 tus, Src. &c. 



Below this point the sloping sides of the escarpments are obscured 

 by accumulations of the detritus of the superior formations, and the 



