1857.] RUCKMAN— OOLITES. 121 



Section at Shorncot, near Cirencester. ft. in. 



1 . Soil, mixed with clay-debris of Oxford Clay 3 6 



2. Cornbrash, more or less mixed with marly bands . . 5 



3. Ragstone, to bottom of quarry. 



Along the line of section its thickness can be ascertained with the 

 greatest nicety, as the slightest depression causes the growth of 

 rushes, indicating Forest Marble ; and here deep ditches may be 

 observable along the strike of the latter, which are useless and in- 

 operative on the porous Cornbrash. 



The section at Mr. E. Bowly's farm, Siddington, is a very interest- 

 ing one, as the ground is considerably faulted ; the fault as usual 

 running along what has since become a valley of denudation. 



The upper bed of this rock, when fresh quarried, is exceedingly 

 hard, but, when filled with fossils, it soon crumbles down under the 

 action of the atmosphere ; if, however, the fossils are few in the rock, 

 it remains intact, and has the harsh intractable feel of the rough 

 Trigonia-grit of the Inferior Oolite, which it so much resembles. 



The lower bed bordering on the blue Forest Marble clays are 

 mostly blue-centred, but usually full of fossils, which is seldom the 

 case in the middle of this thin stratum. 



2. This rock is of great palseontological interest, not only from 

 the extensive list of species to be found in so thin a bed, and the 

 usual great abundance of these ; but principally for the fact that so 

 large a proportion of the fossils (and those too of commonest occur- 

 rence) are identical with species in the Inferior Oolite ; and yet, in 

 as far as my observations of the British Oolites have extended, 

 these species are not usually to be traced in the beds intermediate 

 between the Inferior Oolite and the Cornbrash. 



In appending an analysis of these fossils, I would observe that, 

 though this bed has a tolerably wide range in the neighbourhood of 

 Cirencester and Fairford, yet it is astonishing how few new workings 

 are commenced, — the fact being, that the stone was formerly much 

 used for road-material, but improved transit has caused better mate- 

 rials to be brought from a distance ; so that my list of fossils has 

 been made up from a few and very shallow openings. The follow- 

 ing is a 



Summary of the Cornbrash Fossils. 



Species common 

 Species in the to the Inferior 

 Cornbrash. Oolite and the 

 Cornbrash. 



Cephalopoda 8 6 



Gasteropoda 10 3 



Conchifera 30 21 



Brachiopoda* 8 3 



Echinodermata 8 ....... 8 



Zoophyta 3 ? 



Annelida 4 4 



71 45 



* This is the number according to Mr. Davidson's determination ; I still, how- 

 ever, include several as synonyms. These are as follow : — 



