858 REPORT — 1898. 



Bajocian of tlie Sherborne district' marks the commencement of a new era, 

 where the importance of minute chronological subdivisions, based upon the 

 prevailing- ammonites, is insisted on with much emphasis. This sj'stem he con- 

 siders to be almost as true for the Inferior Oolite as fur the Lias. 



There can be no doubt that its application has enabled Mr. Buckman to effect 

 satisfactory correlations between the very different deposits of the Cotteswolds and 

 those of Dorset and Somerset. In subsequent papers also he brings out an 

 important physical feature — viz. the amount of contemporaneous denudation which 

 has affected deposits of Inferior Oolite age in this country. This serves in part 

 to explain the absence of well-known beds in certain areas. For instance, in the 

 Cotteswolds contemporaneous erosion has, prior to the deposition of the Upper 

 Triffonia-gvit, cut right through the intervening beds, so as to produce in the 

 neighboui-hood of Birdlip a shelving trough 6 miles wide and about 30 feet deep. 

 Thus the extensively recognised overlap of the rarki/mom-zone is accentuated 

 in many places. 



We have a farther 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. Recenth', owing to the investiga- 

 tions of Messrs. Buckman and Wilson,'- this apparent anomaly has been removed, 

 whilst beds of Middle and Upper Lias age, and even Midford Sands, have been 

 recognised. In tliis 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 opa/i?n<s-zone to 

 the Parki/iso/ii-zone inclusive are shown with much detail ; whilst the position of 

 the chief fossil-bed in time tand place has been well established. The general resem- 

 blance of the Dundry fossils to those of Oborne, which I could not fad. to notice in 

 working out the Gasteropoda of the Inferior Oolite, now admits of explanation. 

 Although the quondam Humj)Jiriesiaims-zoii& is richly represented, jet the particular 

 Hum2yhriesia7ium-)ietaer& is held to be absent at Dundry. But if there is a 

 Soiverbyi-hed 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 Sonnininse. 



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 

 hemerse, 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 pur- 

 poses of general classification. Mr. Buckman has earned the right to put forwards, 

 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 kaleidoscope revolves, this formation is perpetually made to assume different 

 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 Oolite on 

 Dundry Hill resemble that of the neighbourhood of Sherborne, both in litholog}'' 

 and fossils, rather than that of the Cotteswolds, only a few miles distant ? 



Nine years ago Mr. Buckmau offered an ingenious solution of this difficulty ; ^ 

 though his recent investigations at Dundry, and especially his appreciation of the 

 effects of contemporaneous erosion, may have caused him to alter his views. Like 

 most people who wish to account for strong local differences, he placed a barrier of 

 Palaeozoic rocks between Dundry and the southern prolongation of the Cotteswold 



' Quart. Jovrn. Gcol. Soc. vol. xlix. (1893), p. 479. 



= Quart. Journ. Gcol. Siir. vol. lii. (1897"), p. 669. Cf. also Pnw. Brid. Xat. Soc. 

 vol. viii. (1897), pt. ii. p. 188. ^ Proc. Cuttcs. Club, vol. is. (1890), p. .S74. 



