20 Remarks on the Great Oolite at Minchinhampton. 



in those works, a considerable number being from the coral rag of Hoheng- 

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

 univalves, the general resemblance to the Minchinhampton shells is so great, 

 that at first wo feel prepared to identify 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 d< ficiency 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 quarri< s to the north and west of the 

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

 univalves can hardily be separated; but in the upper and middle sub- 

 divisions, to the fast of the town, we can obtain but few, and thbse 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 however 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 Ootteswoids during a period 

 in which deposits 200 feet in thickness were formed, and the simultaneous 

 appearance of a large number 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, reasoning would be 

 little better than conjecture ; I have therefore rather preferred to state facts 

 as they are presented to my notice, reflecting that every such contribution, 

 however insignificant, 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 tertiary aera, their paucity in the Great Oolite of 

 Minchinhampton would lead us to infer that some peculiar conditions of 

 sea-bottom existed at that locality which were unfavourable to their in- 

 crease. But so far from the carnivorous Trachelipods " not having existed 

 prior to the commencement of the tertiary aera," we here find them in the 

 middle of the secondary deposits in great force and variety, forming in fact 

 a considerable proportion of the whole number of univalves, and conse- 

 quently existing long before the extinction of the Ammonites and Belem- 

 nites. 



It is highly probable that Dr. Buckland would not now adhere to the 

 above theory, stated some ten or eleven years ago ; but having the authority 

 of his nnme and occurring in a standard work, it still passes current with. 

 the reading public, and has frequently been quoted by subsequent writers. 



On a future occasion I anticipate the pleasure of presenting to the Club 

 some remarks more in detail on the new or less-known molluscous forms 

 which occur in this formation. The Inferior Oolite within the narrow 

 limits of my observation has likewise yielded a considerable store of novel 

 materials for investigation : these would require a separate communication. 



