150 7F". H. Hudleston — On the Yorkshire Oolites, 



sort of calcite, whicli has been more favourable to the preservation 

 of ornament than is usual in beds below the Corallian. The matrix 

 may be described as a hard greyish marlstone, sometimes ferruginous 

 and frequently flecked with large oolitic granules ; sometimes it is 

 stained red from peroxidation of the iron. Portions of this bed are 

 a mass of spathic matter from the abundance of shells. 



The so-called shales of the Cornbrash succeed, and these pass in- 

 sensibly into the soft yellow base of the " Kelloway Eock," which, 

 at Scarborough, and thence throughout the whole of the Tabular 

 Hills to the western escarpment overlooking the ceutral plain of 

 Yorkshire, represents a huge sand bank at the base of the Oxfordian. 

 Q'owards the upper part of this lies our 



5. Fifth zone usually known as the Kelloway Eock. Bivalves, 

 especially Trigonias, are by no means uncommon in the middle 

 portions of the Kelloway Eock, but the great shell beds in which 

 alone recognizable Gasteropoda are found are always on the top. 

 For further information relative to the Kelloway Eock I must again 

 refer to the "Yorkshire Oolites." ^ (For some of the more charac- 

 teristic Cephalopoda see table.) The matrix of these shell-beds is 

 extremely variable, partly in consequence of atmospheric influences 

 — so variable indeed that fossils from this horizon have puzzled and 

 deceived many collectors. There is a bed of fine-grained calciferous 

 sandstone for instance, called the chert bed by Mr. Leckenby, which 

 yields fossils so similar in condition to those of the Lower Calcareous 

 Grit in Cayton Bay, that only a very close inspection suffices to 

 separate them. Another frequent matrix is an ochreous sandstone, 

 a third a greyish ferruginous sandstone, in places stained red, and 

 charged with large oolitic granules. 



Sixth zone. — The lowest bed of the "Oxford Clay" of Scarborough 

 Castle Hill contains numerous fossils (see table for some of the 

 Cephalopods). It seems to have some relationship with a peculiar 

 bed at Cunstone Nab (Gristhorpe) now concealed by a landslip, 

 which yielded many varieties of Ammonites to Mr. Leckenby in a 

 " thin band of calcareous pisolite," and which were always added to 

 the score of the Kelloway Eock. As regards the bed to which I 

 now refer, on Scarborough Castle Hill no specimens of the ornati 

 are ever found in it. The fossils are not well preserved. There 

 are numerous specimens of a Perisphinctes ammonite, whilst the 

 cordati are represented by what is probably Am.. Lamherti. Am. 

 oculatus also occurs and several others. This may be i-egarded as 

 the first of the Oxfordian zones which succeed the ornatus-heA&. The 

 rest of the Oxford Clay contains no definite shell-bed, and the upper 

 portions are almost as devoid of shells as the sands of the estuarine 

 series. This desert region may be regarded as the boundary between 

 the Brown and the White Jura in Yorkshire. 



' " Kellaways Eock" of the Survey Memoir, " Kelloways Eock" of Phillips, 

 "Kelloway Eock" of Leckenby. I prefer the latter name as individualizing a 

 formation of greater importance and wider range in time than the bed which so in- 

 adequately represents it in Wiltshire. 



2 Proc. Geol. Soc. vol. iv. p. 364. Cf. also Leckenby, Q.J.G.S. 1858, p. 4 et seq. 



