14 



sively received some direct or incidental notice at the hands of 

 investigators. The two former, however, have become classical 

 in the annals of Geological investigation, having received the 

 earliest and most marked attention, arising doubtless from the 

 favourable nature of the exposed sections, and the difficulty also 

 of clearly understanding them, as well as the remarkable assem- 

 blage of organic remains which occur in the black, grey, and 

 brown Marls and Shales, &c., which make up the mass of strata 

 above the Eed Marls at the base of both sections. All these 

 conditions of late we have been able more fally to understand, 

 and also to correlate with a similar order of things in many parts 

 of the continent; and thus our own Severn Valley sections — those 

 of Gloucester and Somerset — stand unrivalled, both on physical 

 and palseontological grounds. I need only instance the truly 

 grand sections of Pennarth and Watchett, Uphill and Purton, 

 which, with those above mentioned, are unequalled in Great 

 Britain and elsewhere, save on the flanks of the Rhsetian Alps 

 and parts of Lombardy. A memoir may be written on either of 

 the sections named, and a slight one has been attempted, 

 descriptive of the Garden Cliff or Westbury section,* in which 

 the chief facts were successively detailed, and their relation to 

 other sections in the County alluded to. 



I now attempt to compare the Aust section with that of 

 Westbury ; and although they are similar in many respects, yet 

 in others they differ. 



Aust. — The first authentic notice of Aust CHff occurs in the 

 Trans, of the Geological Society, Vol. 1, (see Series p., pi. 37,J in 

 Messrs. Bxjckland and Conybeare's Observations on the South 

 Western Goal District of England ; and afterwards by Sir Henry 

 • DE LA Beche and Mr. W. Sanders, in Mem. Geo. Surv. Great 

 Britain, Vol. 1, 1846, p. 253. It has been incidentally mentioned 

 and partly described by many since, when treating of the 

 distribution of the Lower Lias, Avicula contorta zone, or Ehsetic 

 beds, of which we now know its chief mass to be composed. 



* Read at Gloucester, March 29th, 1865. 



