1850.] R. N. MANTELL ON THE OOLITE OF WILTS. 311 



Mr. Morris with his accustomed liberality and kindness has care- 

 fully examined the fossils collected by me in these cuttings, and also 

 the rich collection of Mr. Macneil, of Trowbridge, and has drawn up 

 the lists that accompany this paper, and which constitute its most 

 important feature. 



The subdivisions of the Oolite traversed by our operations were the 

 following : 



Portland Limestone, 1 . ... xir ^n en. 4.- 



T^. . -, ^T ' > m a cuttma; near Westbury fetation. 



Kimmeridge Clay, J 



(Coral rag wanting.) 



K 11 ^' h ! in a cutting in the neighbourhood of 



f^ u \ ' I Trowbridge. 



Lorn brash, J ° 



Forest Marble, 1 . t, i, r ^i. 



T> np 1 ^1 ' occurrms; on a branch Ime, three 



Bradiord Clay, > -i i ^ t» li? j 



Great Oolite, j ""les long, to Bradford. 



The Lower Greensand is exposed at Westbury Station. 



The Wilts and Weymouth branch of the Great Western leaves the 

 main line at Thingley, a village half way between Chippenham and 

 Corsham, and takes a southerly course to Westbury, a distance of 

 fifteen miles, where the line terminates at present. 



At Thingley the rock exposed in the cuttings of the Great West- 

 ern is the Cornbrash, which extends over a large area of the neigh- 

 bouring country, including Chippenham. This rock appears in the 

 Wilts and Weymouth cuttings for a mile and a quarter, and then, on 

 the opposite side of a steep valley, rises rapidly and crops out ; the 

 remainder of the section, which is about 1 1 chains long and 20 feet 

 deep, exposing the lower beds of the Cornbrash, and the marls and 

 shales of the Forest marble. After crossing another high embank- 

 ment, the Cornbrash reappears at the entrance of the cutting, dipping 

 rapidly, and it is not again visible till we reach Trowbridge, nine 

 miles and a half from the junction with the Great Western. 



After losing the Cornbrash at the second mile, the line continues 

 nearly the whole way to Staverton, at the seventh mile, on embank- 

 ments, keeping along the valley of the river Avon. This valley is 

 covered with a bed of gravel from 4 to 1 8 feet in thickness, and from 

 half a mile to a mile and a half in width, and in it are found boulders 

 and pebbles of numerous varieties of primary and secondary rocks, 

 and rolled fossils of the Oxford clay and Kelloway rock. Mounds of 

 the Oxford clay occasionally protrude through this accumulation of 

 water-worn materials. 



At Staverton the line crosses the river Avon, and leaving the val- 

 ley, enters a series of cuttings in the Oxford clay and Kelloway rock, 

 which extend to the 9^ mile, near Trowbridge. It was from these 

 cuttings, averaging 14 feet in depth, that I obtained the greatest 

 number of Ammo7iifes Kcenigi^ Ancyloeeras Calloviense, &c. 



At seven miles and a half the railway crosses the river Biss, where 

 the Section fig. 1 commences. 



The Cornbrash reappears on the other side of the Biss, and the 



