17 



6 



5 



16 Lower Pecten Bed. Blue, hard, grey, shelly Lime-' 



stone, evenly bedded, and full of the ordinary 

 Rhaetic Fossils, Av. contorta, Pecten Valonien8is,\ 8 

 Cardium Rhceticum, Pullastra, Anatina, Aximis, | 

 Anomia, &c. ...... 



17 Black Shales, (Avicula Shales,) with Axinus, ^ 



Cardium Rhceticum, A vicula contorta, Pullastra, | 

 occurring in definite lines. An indurated band > 

 divides these Shales from some of those above, | 

 but its inconstancy makes it advisable not to | 

 separate the Shales. Together they measure J 



18 Upper Pecten Bed. Hard grey Limestone, con- 



taining Fish Scales, Pecten Valoniensis, Placu- 

 nopsis Alpina, Pleurophorus elongatus, dx. 

 .19 Black Shales, highly laminated . . . .50 

 A space of some 13 or 14 feet occurs here, which, 

 from the nature of the cliff, could neither be measured nor 

 critically examined. They are grey and white Marls, 

 with nodular Limestones, and I doubt not occupy the 

 place of the White Lias, and are the equivalents of beds 

 numbered from 14 to 19 in my Westhnry section, as the 

 Cotham Marble occurs at the top of these Marly beds, 

 and immediately upon it occurs the Ostrea beds of the 

 Lower Lias, as at Westbury. 



There is one featiire in Aust, with relation to its physical 

 structure, which is of importance, and contra-distinguishes it 

 from its neighbour Westbuiy, viz., that the two Pecten beds are 

 thick hard grey crystalline bands, whereas at Westbury no 

 Limestone whatever is found below the Estheria Zone or Monotis 

 beds ; in this respect Aust is allied to Pennarth, Patchway, 

 Watchett, and the series south of Weston-super-Mare, where the 

 Valoniensis bands are very thick. 



The chief difference between the Aust section and Westbury 

 consists also in the absence of the Pullastra beds at the base, 

 and which are a most marked feature at the latter place; and 

 again in the absence at Aust of the Estheria Zone, unless it be 

 covered at the top of the section. Another remarkable circum- 

 stance is also observable in the fossil contents of the Bone bed, 

 from the fact of the total absence of the remains of Ceratodd at 



