294 MR. H. B. WOODWAED ON A WELL-SINKING AT SWINDON. 



Mr. R. Damon, which has yielded a considerable number of fossils *. 

 That layer, however, is regarded as the top of the Corallian beds by 

 Messrs. Blake and Hudleston, and should no doubt be placed on that 

 horizon. The fossils found in the Swindon bed are not sufficient to 

 enable any palaeontological comparison to be made ; but when we 

 compare the Swindon section with that at Highworth, about six 

 miles to the north-east, we might be disposed to put more than we 

 have included with the Corallian rocks at Swindon. 



The general section at Highworth has been represented as follows 

 by Messrs. Blake and Hudlestonf : — 



ft. in. 



CoralEag 1 



Oolitic Flags and Sandy Clay 11 



Shell-bearing gritty beds (Main Limestone) 12 



Hard Band 2 



Loose Calcareous Sands 14 



Clay ? and Sands in alternations 70? 



110 



It is therefore quite possible that the iron-shot limestone at 

 Swindon may represent the " Coral Rag " in the above section, and 

 the clays beneath may represent the " Oolitic Plags and Sandy Clay." 



During the early portion of the well-sinking at Swindon very 

 many specimens were not preserved. Moreover, from the main mass 

 of the Corallian series no determinable fossils were collected. But the 

 character of the record suggests that the lower beds at Swindon are 

 not so thick as Messrs. Blake and Hudleston represent them to be 

 at Highworth, although their estimate, of a total thickness of 110 

 feet, includes 70 feet of clay and sand, which they insert with doubt. 



At the same time, throughout the south-west of England (to con- 

 fine my remarks to the area with which I am acquainted) the 

 Kimeridge and Corallian beds are so intimately linked together, 

 both lithologically and palaeontologically, that we cannot fix a 

 boundary between the formations which can be traced with precisiou. 

 Nor need we be at all concerned at our failure ; for nature could not 

 be expected to fix rigid limits either for the accumulation of sedi- 

 mentary strata or for the entombing of organic remains. Since' 

 writing the above remarks, I find that Mr. Hudleston has observed 

 that " the name Corallian must be deemed a mere matter of con- 

 venience, not representing a formation in time " J. 



The Oxford Clay, as before mentioned, is 572 feet in thickness. 

 Many fossils have been obtained, and these are grouped together as 

 coming between certain depths, although we have no reason to draw 

 definite lines. Broadly speaking, however, the record furnishes 

 evidence of the Callovian fauna at the base, and of the incoming in 

 succession of the " ornatus " and " cordatus " types of Ammonites. 

 And it is satisfactory to find the ordinary succession of Ammonite- 



* See ' Geology of Weymoutb/ &c. New edition, 1884, p. 65. 

 t Quart. Journ. Geol. Soc. vol. xxxiii. p. 272, and Table, p. 404. 

 X Proc. Geol. Assoc, vol. v. p. 409. 



