[NTRODUCTION. 9 



wore obtained, is about a mile and a half north-west of Road, and here, opposite 

 the lodjge, is an overgrown quarry in Forest Marble, but a little further up the 

 hill the surface of the ground is strewn with Cornbrash fossils. At Trowbridge 

 all the openings are now closed, and those available in L850 ('Quart. Journ. 

 Greol. Hoe.,' vol. vi) are no longer so, which is unfortunate, for three species of 

 Ammonites were recorded therefrom. At Hilperton all the former openings 

 are now covered with market gardens. Probably most of the fossils there 

 obtained belong to the Forest Marble. The rocks at Laycock, whence Mr. 

 Walton, of Bath, recorded many fossils, are now referred on the survey maps 

 to the Forest Marble likewise. But at Westwood there is a broad spread of 

 Cornbrash all over the village, seen in the roadside banks, especially towards 

 the west, where six feet of rubble is shown. At Thingley also, nearer Chippenham, 

 there is a shallow opening of the usual type. 



8. At Folly Faem, opposite the ninety-sixth milestone on the road from 

 London to Bath, is a very instructive quarry showing a long face of considerable 

 depth, referred to by E. Hull ('Greol. of Parts of Wilts and Gloucestershire,' 

 Geol. Surv. Sheet 34). In this the following section is seen : 



Ft. in. 



1. Hard brown denticles of stone (weathered) on the west side only . 10 



2. Brash mixed with clay . . . . . .08 



3. Broken up, very irregular, brash . . 10 



4. More solid brashy limestone . . . . . 2 



5. More solid limestone, with a base of mingled material full of Myacites casts 1 



a. Brown laminated earbonaceous clay with drift-wood 



2 in. at each end, increasing at the west to . . .22 



b. Shelly layers of Forest Marble with intervening clays characterised by Terebratula 



majcillata and Lima cardiiformis . . . . . 10 



The most remarkable features in this section are the thinning out of the 

 clay Bed a in so short a space, suggesting a local unconformity, and the 

 absolute distinction of the fossils of Bed b from those of Nos. 1 — 5. These 

 latter alone, which are all of a brashy character and contain abundance of 

 Avicula echinata, are taken to represent the Cornbrash, and the quarry is 

 considered as a justification for a similar separation elsewhere. The Beds Nos. 

 1 — 3 are the most easily broken up and the most fossiliferous, and Nos. 4 and 5 

 more solid and less fossiliferous. In the numerous shallow openings of the 

 neighbourhood and elsewhere the Cornbrash is sometimes of the character of 

 Nos. 1 — 3 and sometimes of Nos. 4 and 5. In the latter case the upper three 

 beds have probably been washed away, as, for instance, in the shallow opening 

 at Biddestone close by. 



9. OiiiTKXiiAM is a name often used, but there are at the time of writing 

 few satisfactory openings, and these are usually only temporary. 1 Nevertheless. 



1 Since the above was written one has bees opened up. 



2 



