1857.] BUCKMAN — OOLITES. 129 



From these data I infer that the Portland Oolite at Swindon is about 

 40 feet in thickness, and capped by about 18 feet of Wealden beds. 

 It is not my intention to enter into a discussion about the Wealden 

 character of these upper beds* ; I, however, quite agree that they 

 are simply the outliers of a rock which assumes great importance 

 farther south, as in the Vale of Wardour, where they have been so 

 successfully worked and ably described by Dr. Fitton and my friend 

 the Rev. P. B. Brodie. 



As regards the fossils of the Portland rock, these will be found to 

 be highly typical of an Oolitic deposit ; and, if they be compared 

 with those of the true Chalk, the latter would seem to indicate a 

 sudden and extraordinary change in the fauna ; the passage is, how- 

 ever, after all, tolerably gradual from the Oolites to Chalk, through 

 the medium of the Greensand, such fossils as the Trigonia, Pano- 

 paa, Cardium, Pinna, and Perna being at least important genera 

 common to both Greensand and Portland Oolite. 



The following list of fossils of the Portland at Swindon, all of 

 which I have obtained from the large quarry, are mostly determined 

 from Dr. Fitton' s list and illustrative engravings ; they consist of 



Ammonites giganteus, M.C. Trigonia gibbosa, Fitton, pi. 22, f. 4. 



biplex, M. C. species ? 



Terebra Portlandica, Fitton, Mem. pi. Lucina Portlandica, id. pi. 22, f. 12. 



23, f. 6. Cytherea rugosa, Fitton, pi. 22, 

 Natica elegans, id. pi. 23, f. 3. f. 13. 



Buccinum naticoides, id. pi. 23, f. 4. Cardium dissimile, M. C. 



angulatum, pi. id. 23, f. 5. Perna quadrata, M.C. 



Nerita angulata, id. pi. 23, f. 2. Panopaea depressa, M. C. 



Trigonia incurva, Benett, Wiltsh. Foss. Pecten lamellosus, M. C. 

 t. 18, f. 2. 



Large masses of coniferous wood are often found on the Portland 

 measures ; and occasionally well-preserved trunks of trees are ex- 

 humed at the Swindon quarries. 



Here, then, I must content myself for the present with having 

 described the more general characteristics of all the members of the 

 Oolitic series of rocks ; it will, however, be seen that the discussion 

 of physical changes, such as a description of the many faults by 

 which the country under review is intersected, the facts connected 

 with our numerous valleys both of denudation and depression, the 

 drifts by which the country is overspread, and which are so diverse 

 in character, and other interesting physical phenomena have been, 

 for the most part, unnoticed. This, however, is not from inatten- 

 tion to such important matters, but from want of time to put my 

 notes together ; and so, for such matters, as also for a comprehensive 

 list of fossils of the Oolites, now in course of preparation, I must 

 beg indulgence until the next session of our Society ; indeed, from 



* Besides Dr. Fitton's paper above referred to, see Mr. Brodie's and Mr. Aus- 

 ten's Notices of these beds, Quart. Journ. Geol. Soc. vol. viii. p. 53, and vol. vi. 

 p. 467. 



VOL. XIV. PART I. K 



