ix. THE WESTBURY SECTION. 103 



Strata. ft. in. 



Lumpy grey shale . . . . , o J pu 



Dark shale 4 o L 



Arenaceous shelly band . o i Pullastra, Cardium. 



Shale 2 3 



Bone grit ..... o o^ Pullastra. 



Dark shale 39 Pullastra, Tooth. 



Dark thinly-laminated shale . .14 (No fossils.) 



Dark shale 2 3 Pecten Valoniensis. 



Pyritous Bone grit . . . .01 Acrodus, Saurichthys, &c. 



Dark shale I 5 Saurichthys and other fishes. 



Bone grit, ripple marked I o Bones frequent. 



Dark shale . . . . .23 Fucoids. 



Skerry laminae, bones . ..03 Pecten, Pullastra, Bones. 



Dark shale 14 



Total thickness of Rhaetic beds 34 6 



POIKILITIC. 



Grey marls 18 o 



Red and grey marls . . . . 30 o 



The appearances are not quite the same, and the measures are 

 somewhat unequal in different parts of the cliff. 



In this section it will be observed that the uppermost thin layers 

 of limestone are left to the liassic series, the rhaetic ending with 

 the higher Pullastra shale. This is not the classification adopted 

 by the Geological Survey, which includes the Monotis bed in the 

 rhaetic group. There are reasons for each of these methods. On 

 the supposition that the whole group is to be treated as to some 

 extent independent both of trias and lias, as Mr. C. Moore's re- 

 markable discoveries b in Somersetshire seem to require, it will be 

 often useful to include with the rhsetics the lowest members of 

 true lias. But, if we wish to mark by a strong line the distinction 

 of the two groups, it will be convenient to give, as Dr. Wright 

 does, and as Mr. Brodie approves, the Monotis, or Insect or Guinea 

 bed, to the lias. It is, in fact, the lower or ' bone-bed ' series, with 

 Pullastra arenicola, which manifests the principal affinity with the 

 triassic deposits. 



The calcareous band at the base of the Estheria bed, sometimes 

 constituting a great part of that bed, is much alike in some respects 

 to the so-called landscape stone of Gotham, near Bristol, and is 



b On Rhsetic Beds and Fossils. Quar. Journ. Geol. Soc. vol. xvii. p. 483. 



