THE CORALLIAN ROCKS OF ENGLAND. 387 



we obtain the reverse of the Forge -valley section, where it is the 

 two limestones which are on the point of uniting. No certain indi- 

 cations of the Middle Grit are to be seen in the Howardian Hills. 



The Upper Limestones, which are not seen on the coast at all, 

 except in an altered and fragmentary form, peeping from beneath 

 the drift of Filey promontory, are throughout divisible into Coralline 

 Oolite and overlying Rag ; and they are, on the whole, much more 

 fossiliferous than, and never contain the Brachiopoda of the Lower 

 Limestones. The Coralline Oolite, underlying the Rag in the great 

 crescent of rocks which sweeps round the western half of the vale 

 from Pickering to Malton, is fossiliferous in certain beds, which are 

 generally characterized by the great abundance of Chemnitzia. It has 

 two petrological types, the oolitic and the pasty ; and its rocks are 

 for the most part mixtures of these in varying proportions ; but the 

 variation in the character of the Coralline Oolite is not sufficiently 

 marked to be here recapitulated. The Coral Rag has several 

 different types. In the Scarborough district the absence of Cidaris 

 florigemma from the Rag, and the interesting group of small univalves 

 which it contains, give it a peculiarity ; but whether this is due to the 

 nature of the coral, in this district confined almost exclusively to 

 Thamnastrcea concinna and Khabclophyllia, or to deposition in a sepa- 

 rate basin, is not clear. When we meet with the Rag in the next (or 

 Pickering) district, it is seen to be crowded with the spines of the 

 characteristic urchin. Besides the ordinary form, we have a solid and 

 compact form at Helmsley, which is highly siliceous, as, indeed, are 

 most of the Rags ; a beautiful free limestone at Hildenley ; a strange 

 medley at Sike Gate, near Cawton, where the fossils are very pecu- 

 liar ; and a very distinct type on the east of the Derwent (section X.), 

 where, including the entire limestone series, there is a thickness 

 of 100 feet, some portion being intercoralline, and containing an 

 extraordinary profusion of urchins, as well as a rich molluscan 

 fauna, of such a character as to indicate the possibility of this Rag 

 being of slightly later date than that of the Tabular Hills. 



The development of the supracoralline beds is copious and tolerably 

 regular. In an arenaceous form, as Upper Calcareous Grit, these 

 beds attain their maximum thickness in the extreme western bay of 

 the vale of Pickering, where they may be seen in several places to 

 rest upon the indurated surface of the Coral Rag. Eastwards, how- 

 ever, a peculiar argillo- calcareous deposit, less constant as a forma- 

 tion^ observed to intervene between the Coral Rag and Upper Calca- 

 reous Grit, the base of which at Pickering itself is also very muddy. 

 The Upper Calcareous Grit of Yorkshire possesses features which 

 can seldom be mistaken, and contains a series of fossils at least par- 

 tially Kimmeridgian. There may be room to doubt the evidence of 

 " biplex" Ammonites ; but such forms as A. alternans and A. Ber- 

 ryeri are more satisfactory. A. varicostatus still seems to be 

 present. In the Howardian Hills no Upper Calcareous Grit comes 

 to the surface; but the great deposits of Burdale, overlying the 

 North-Grimston Rag, contain several of the fossils of the Upper 

 Calcareous Grit of Pickering. 



2c2 



