120 Remarks on the Great Oolite of Mincltinhampton. 



one-half the entire number of bivalves can be identified in those 

 works, a considerable number being from the coral rag of Ho- 

 henggelsen, which seems to be the equivalent of our Great Oolite. 

 Among the univalves, the general resemblance to the Minchin- 

 hampton shells is so great, that at first we feel prepared to iden- 

 tify the greater number of them ; a closer scrutiny undeceives 

 us, and ultimately we are surprised at the very few which we can 

 call our own. It may be suspected indeed, that the meagre lists 

 of univalves hitherto published relating to the formation in 

 question are the result, not so much of an actual deficiency of 

 those shells, as of the difficulty of separating them from the stone 

 in a condition sufficiently well-preserved to admit of specific 

 characters being recognized. The oolite of our district itself 

 furnishes an instance in illustration ; almost the entire suite of 

 univalves are procured from quarries to the north and west of 

 the town, and even within those limits are certain localities from 

 which the univalves can hardly be separated ; but in the upper 

 and middle subdivisions, to the east of the town, we can obtain 

 but few, and those only which approach the globular figure, as 

 Natica and Bulla, usually in the form of casts ; with slender 

 spiral shells the attempt is hopeless. These circumstances how- 

 ever are altogether independent of the great fact forced upon 

 our attention, — viz. the scarcity and almost entire disappearance 

 of the Cephalopoda from the sea of this portion of the Cottes- 

 wolds during a period in which deposits 200 feet in thickness 

 were formed, and the simultaneous appearance of a large num- 

 ber of new and more simple forms to supply their place. 



With our present very scanty knowledge of the circumstances 

 which conduce to change of species on the floor of the sea, rea- 

 soning would be little better than conjecture ; I have therefore 

 rather preferred to state facts as they are presented to my no- 

 tice, reflecting that every such contribution, however insignifi- 

 cant, is something added to the general store of knowledge, and 

 consequently an aid to our conceptions of the operation of that 

 infinite and all-pervading wisdom which is exemplified equally 

 in the lowest as in the highest beings of creation. 



Hence, though it is well known (as above-quoted from Dr. 

 Buckland), that throughout the vast deposits of the secondary 

 rocks those important tribes of Cephalopods, the Ammonites and 

 Belemnites, reigned supreme amongst the molluscous races, and 

 that they became extinct prior to the commencement of the ter- 

 tiary sera, their paucity in the Great Oolite of Minchinbampton 

 would lead us to infer that some peculiar conditions of sea-bot- 

 tom existed at that locality which were unfavourable to their 

 increase. But so far from the carnivorous Trachelipods "not 

 having existed prior to the commencement of the tertiary fera," 



