THE CORALLIAN ROCKS OF ENGLAND. 



381 



calcareous bands, divided by softer subcalcareous shales. The shales 

 burn to a whitish brick, but without any of the properties of a 

 fire-brick. The hard stone yields a good hydraulic mortar, lately 

 much used for the Scarborough aquarium. The formation is the 

 probable equivalent of the entire upper series of Pickering ; and 

 the fauna has strong analogies with that of the Upper Calcareous 

 Grit as there developed, especially in the great abundance of the 

 same forms of Lucina. The Ammonites also fairly correspond, as 

 far as it is safe to judge where the state of preservation is so in- 

 different. Subjoined is a list, the determinations to be received 

 with a qualification. 



Belemnites hastatus ?, Montf. 

 *nitidus, Dollf. (B. explanatus, 



Phil). 

 Ammonites biplex-varicostatus. 

 , sp. {cf. alternans, Von Buck, 



serratus, Sow.). 

 Gryphcea subgibbosa, Bl. §• H. 

 Pecten vimineus, Sow. 



Pinna, sp. 



Avicula, sp. 



Lucina aspera, Buvig., common. 



' ?P* 



Thracia depressa, Phil. 



Pholadomya, sp. {cf. concentrica, 



Rom.). 



Goniomya literata, Sow. 



The conditions being different, the fauna of the Coral Eag has for 

 the most part disappeared, whilst that of the regular Kimmeridge 

 Clay has not yet fully set in. There can be very little doubt that 

 such beds are the result of the grinding-down of masses of Corallian 

 limestone, whose debris, largely mingled with the argillaceous mud 

 now invading the sea, no longer coralligenous in this particular 

 area, went to form banks of bastard limestones, which have probably 

 only a limited range, forming a fringe, as it were, round reefs which 

 have been wholly or partially destroyed during the interval marking 

 the close of the Corallian conditions in the Oxford-Kimmeridge 

 sea. 



As a formation the supracoralline limestone has considerable 

 extension in the valley at the foot of North-Grimston Wold ; and 

 further westward it is to be found in the low ground between 

 Langton Wold and Birdsall. Near the latter village it may be seen 

 faulted against the Lower Calcareous Grit at Rowmire Spring ; and 

 in this way the Lower Calcareous Grit is again brought in, now 

 occupying its normal position, which in the Howardian Hills should 

 be to the S.S.W. of the Corallian limestones. 



Summary. 



We will here recapitulate the results that our detailed study of the 

 Corallian rocks in the above districts have produced, and would refer 

 to our Table of Comparative Sections (PI. XII.) for their illustration. 



Weymouth district. — We have here three principal localities, 

 the development in which is represented by our sections Nos. L, II., 

 III. The most complete series is in the neighbourhood of Wey- 

 mouth itself (section I.), where, in ascending order, we have the 



* This is rather stouter than the usual Kimmeridge form, and is inter- 

 mediate between the regular B. nitidus and B. abbrcviatus. 



