Notices of Memoirs — Coal-measures under Oxfordshire. 459 



3. In reference to the size of the Aptychus, it seems natural that 

 it should not exactly fit the aperture of the shell, for if it did the 

 animal would have to be continually opening the lid to obtain fresh 

 water ; while if there were abundant space between the operculum 

 and the shell-wall, the animal could breathe continuously in a 

 contracted condition, and the presence of " stries creuses " in the 

 test of many Ammonites (produced by the tightening of the muscular 

 walls, so that they were thrown up into little ridges which left 

 their imprint on the inner shell) seems to necessitate the power of 

 doing so. While, again, if the Aptychus were poisonous, as I have 

 suggested, and not merely a passive protection, there would be no 

 necessity for the orifice to be closely shut. At any rate, then, there 

 seems abundant evidence that the Aptychus could perform useful 

 functions as an operculum without having to fit the aperture exactly. 



In conclusion, 1 have shown that the theories against the Aptychus 

 being an operculum can be met with equally plausible ones in 

 favour of that view ; and the fact that the Aptychus is known in 

 one specimen to have officiated in that capacity, ought to throw 

 suspicion on the other theories. 



Abstracts of Papers read before the British Association at 



Oxford, August 9-14, 1894. 

 I, — The Probable Eange of the Coal-measures under the 



Newer Kocks of Oxfordshire and the Adjoining Counties. 



By Professor Boyd-Dawkins, F.K.S. 

 rpHE principle laid down by Godwin-Austen and Prestwich that 

 X the master or tectonic folds in the pre-Carboniferous and 

 Carboniferous rocks are lines of weakness along which the newer 

 rocks have been folded in later times, has been recently applied 

 by Bertrand to the district of northern France. In the present 

 communication the author proposes to see how far it can be used 

 in the search after the buried Coal-fields of the counties of Oxford, 

 Buckingham, Berks, and Wilts. 



From the relation existing between the tectonic anticlines and 

 synclines in the districts of South Wales, Gloucester, and the 

 West of England, where they can be studied at the surface in the 

 Palaeozoic rocks, most important conclusions may be drawn as to 

 the Coal-fields buried under the newer rocks in southern England. 

 They are as follows : — 



1. The Mid-Devon syncline, traceable eastwards until it cuts the 

 sea-line near Bognor. 



2. The North Devon anticline, which runs eastwards through the 

 Vale of Wardour, past Salisbury, and along the anticline of the 

 Weald from Petersfield to Dungeness. 



3. The Mid-Somerset syncline, which sweeps eastward through 

 the Vale of Bridgewater and Glastonbury, through the Chalk downs 

 between Heytesbury and Hindon, to Haslemere. From this point 



