386 J. F. BLAKE AND W. H. HrDLESTON ON 



fossils, A. perarmatus much less so ; but A. Williamsoni is often 

 found in the lower or ferruginous portion of the passage-beds in the 

 neighbourhood of Scarborough. The presence of undoubted forms 

 of A. plicatilis is by no means common. In the Hackness outlier 

 there occurs a well-marked Lower Coral Rag included within the 

 Lower Limestones, and containing the usual species of corals and 

 dwarf forms of some of the associated shells, but without Cidaris 

 florigemma. Amongst its characteristic fossils are Spongia Jloriceps 

 and Waldhehnia Hudlestoni. This Rag is very local ; but its position 

 may be traced at Scarborough and Filey ; and to the west corals 

 may be noted about the same horizon. The Scarborough type of 

 passage-beds seems to be lost in the western portion of the Tabular 

 Hills ; and vast accumulations of cherty beds occupy their place, the 

 tendency to silicification extending upwards even into the oolites. 

 The maximum thickness of the Lower Limestones, all included, near 

 Kirkby Moorside, is estimated by Mr. Fox Strangways at not far 

 short of 150 feet. At Kepwick, on the western escarpment, the 

 oolite of the Lower Limestones (Hambleton oolite) has a thickness 

 of about 50 feet, and thence continues to thin out towards the 

 south-east, disappearing altogether ere we reach the Gilling Coxwold 

 Gap (section XIII.). The revival of this group, as a separate forma- 

 tion, in the Howardian Hills, is somewhat problematical ; but the 

 peculiar phase of passage-beds already noted is seen to be highly 

 fossiliferous at Appleton, and there is a still stronger development, 

 though without so many fossils, in the western suburb of Malton. 

 There are certainly two very different groups of oolite in the neigh- 

 bourhood of that town ; but that which is presumably the lower of 

 the two cannot at present be identified with any portion of the Lower 

 Limestones of the western and northern hills. 



The Middle Calcareous Grit is rather irregular and uncertain. 

 It seems to break out in Filey Briggy but otherwise to have only a 

 feeble development east of Forge valley (section XIV.). West of that 

 meridian it begins to make some show on the surface ; and at Pickering 

 attains probably its maximum development in the northern hills 

 (section XIII.). Here it so much recalls some of the features of 

 the Lower Calcareous Grit as to show how similar must have been 

 the physical conditions which produced it. But the characteristic 

 Brachiopoda of the lower formation are either absent or so rare as 

 to escape notice. At Pickering the higher beds are charged with bands 

 of gritty suboolitic limestone, again constituting a series of upper pas- 

 sage-beds, rich in Trigonux, which form a fitting introduction to the 

 Coralline Oolite. This phase may be traced, wherever there is an 

 exposure, westwards as far as Kirkdale, and perhaps in a modified 

 degree to within a short distance of Helmsley. Along the line of 

 the Hambleton section (section XII.) the presumed equivalent of 

 the Middle Calcareous Grit presents a different appearance ; its 

 thickness may be as much as 60 feet ; but where the Lower Lime- 

 stones are thinning out so much, the true division between this and 

 the Lower Calcareous Grit proper is not always clear. A mile or 

 two further south of this line the two grits seem to coalesce, and 



