as President, to the Geological Section. 467 



erosion has, prior to the deposition of the Upper Trigonia-grit, cut 

 right through the intervening beds, so as to produce in the neigh- 

 bourhood of Birdlip a shelving trough six miles vi^ide and about 

 30 feet deep. Thus the extensively recognized overlap of the 

 Parkinsom-zone is accentuated in many places. 



We have a further instance of good work in the case of Dundry 

 Hill. An inspection of the 1-inch Survey map would lead one to 

 suppose that the Inferior Oolite there rests directly on the Lower 

 Lias. Recently, owing to the investigations of Messrs. Buckraan 

 and Wilson,^ this apparent anomaly has been removed, whilst beds 

 of Middle and Upper Lias age and even Midford Sands have been 

 recognized. In this way the authors claim to have reduced the 

 thickness assigned to the Inferior Oolite on Dundry Hill by about 

 100 feet. In the paper above quoted the vicissitudes and faunal 

 history of the Inferior Oolite from the opaliniis-zone to the Parkinsoni- 

 zone inclusive are shown with much detail ; whilst the position of 

 the chief fossil-bed in time and place has been well established. 

 The general resemblance of the Dundry fossils to those of Oborne, 

 which I could not fail to notice in working out the Gasteropoda 

 of the Inferior Oolite, now admits of explanation. Although the 

 quondam Humphriesianus - zone is richly represented, yet the 

 particular Humphriesianiim-hemera is held to be absent at Dundry. 

 But if there be a Soiverbyi-heA anywhere it should serve to connect 

 these two localities, where, according to Mr. Buckman's phraseology, 

 the principal zoological phenomenon is the acme and paracme of 

 Sonnininee. 



Mr. Buckman, as we have seen, is no longer satisfied with the 

 old-fashioned threefold division of the Inferior Oolite, and his time- 

 table includes at least a dozen hemerge, with prospect of increase. 

 Granting that it would have been difficult to solve the Dundry 

 problem without a detailed knowledge of ammonite horizons, there 

 arises the question as to the utility of such minute subdivisions for 

 the purposes of general classification. Mr. Buckman has earned 

 the right to put forward, if he pleases, the several stratigraphical 

 rearrangements in which from time to time he indulges. The 

 Inferior Oolite has been his especial playground, and, as the kaleido- 

 scope revolves, this formation is perpetually made to assume difi'erent 

 proportions, even to the verge of extinction. But this practice is 

 not without its disadvantages ; whilst the invention of new names 

 tends to clog the memory, and the novel use of old ones is apt to 

 produce confusion. 



We have not quite finished with Dundry yet, since that classic 

 hill serves to illustrate in Mesozoic times a peculiarity of which 

 I have already pointed out two notable instances in this district, 

 where an abrupt and seemingly unaccountable difference is observed 

 in beds which are approximately synchronous. The problem to 

 be solved is this — Why does the fossiliferous portion of the Inferior 



1 Quart. Journ. Geol. Soc, vol. lii (1896), p. 669. Cf. also Proc. Brist. Nat. 

 Soc, vol. viii (1897), pt. 2, p. 188. 



