ANNIVERSARY ADDRESS OF THE PRESIDENT. xli 



Tespectively the Liassic, the Bathonian, and the Oxfordian ; the two 

 latter terms bemg used for want of better, and being adopted in a 

 wide and general sense, and not in the restricted meaning in which 

 they are used by M. Alcide d'Orbigny. The horizon of change of 

 facies at the boundary between each is a horizon, to a considerable 

 extent, of change of species. I believe that every year's research will 

 make it more and more evident that the perishing of species is simply 

 the result of the influence of physical changes in specific areas, and 

 depends upon no law of inherent limitation of power to exist in time. 

 If so, we should expect to find indications of the cause of the greater 

 changes in the oolitic and xnarine fauna in the shape of strata bearing 

 evidence of a wide-spread change of physical conditions within the 

 great oolitic area. An extensive change of species within a marine 

 area in all likelihood is dependent on an extensive conversion of that 

 area into a terrestrial surface. 



Now it is becoming more and more clear that such a change of 

 condition occurred over a very wide area in the interval between the 

 main mass of the middle and upper Jurassic types. The researches 

 of Mr. Morris do much towards completing the demonstration of the 

 nature and extent of these changes in the area now occupied by the 

 British Islands, and it will be seen hereafter, how, even as far away 

 as Italy, we have clear proofs of a similar change of conditions about 

 the same epoch. Much may be done towards clearing up the details 

 of this matter by more extensive and careful investigations of the 

 Scottish oolites, guided by the light that is opening gradually upon 

 us. Indeed I know of no field more likely to yield fresh laurels to 

 the British geological observer than the thorough exploration of 

 Scottish secondary geology. 



In a paper by Professor Buckman, published in the ' Annals of 

 Natural History' for November last, and one of the many interesting 

 contributions to British geology which we owe to that active assem- 

 bly of provincial observers, the Cotteswold Naturalists' Club, the 

 Cornbrash and associated strata of the neighbourhood of Cirencester 

 are described in detail, and under an economical point of view not 

 always attended to, viz. the agricultural value of the soils formed by 

 the several oolitic rocks. Through the predominance of phosphoric 

 acid and sulphate of lime in the Cornbrash, as compared with the 

 'stone brashes' of the Great and Inferior Oolite, the value of the 

 soils in the former rock is considerably greater, as shown by the 

 analyses of Professor Voelcker. Mr. Buckman presents some good 

 facts concerning the distribution of fossils in these beds, and enume- 

 rates twenty-one species of lamellibranchiate bivalves common to the 

 Inferior Oolite and Cornbrash in Gloucestershire, and rare or wanting 

 in the Great Oolite of the district. The recurrence of the species in 

 this instance, as indeed in every similar case, is dependent on the 

 recurrence of similar conditions. In every such case we may, h 

 prio7-i, assume that the intermediate strata, formed under different 

 conditions, somewhere within the area of the ancient marine region 

 to which they belong, change their character, putting on the mineral 

 aspect and containing the peculiar fossils of the superior and inferior 



