Yol. 68.] SUCCESSION IN THE NOETH-WEST OE ENGLAND. 543 



The fossils are well preserved in calcareous nodules in the shale, 

 and the fauna may be compared with that of Dg of Derbyshire ; 

 some of the species (marked with an asterisk) have not been met 

 with elsewhere in the area described in the present paper. 



Among the corals, an interesting occurrence is that of Dihuno- 

 phyllum muirheadi, showing the persistence of this form throughout 

 the Yoredale Series of the Pennine District ; it enters near the 

 summit of the Lonsdalia-floriformis Sub-zone, is found plentifully 

 in several of the higher Yoredale Limestones, especially the 

 ' Great ' Limestone, and is still abundant in the Botany Beds. 

 Another interesting form, practically limited to this horizon, is 

 Phillipsastrcea radiata, which occurs somewhat abundantly in the- 

 upper chert-bearing portion of the deposits. I have never found 

 it in situ at any other horizon, but two specimens were collected 

 as loose blocks. One of these was found resting upon the Tyne- 

 Bottom Limestone in High-Cup Gill, and, as the specimen was quite 

 angular and unworn, may possibly have been derived from one 

 of the overlying Yoredale limestones close by ; the other was 

 found washed out of the drift-deposits in Eavenstonedale, the coral 

 being preserved as a cast in a hard gannister-bed which must have 

 been derived from the higher Yoredale or Millstone-Grit beds of 

 the Pennine Chain on the east or north-east. Outside the jSTorth- 

 Western Province PliiTli]}sastraa is also apparently characteristic 

 of the higher beds of the Dihunophyllum Zone. 



Many of the brachiopods are also characteristic of a high horizon 

 in Derbyshire; and some species as, for instance, Sclielliuienella 

 radialis^ have not been met with at a lower horizon in the North- 

 AVestern Province. 



So far as I am aware, this is the highest truly 

 marine fauna yet met with in the North of England. 

 The appearance of this fossiliferous limestone deposit, overlying a 

 considerable thickness referred to the Millstone Grit by the officers 

 of the Geological Survey, is of some interest. The fauna cannot be 

 considered as a remnant of the local Yoredale fauna that collected 

 here before being completely exterminated : for, not only is the 

 fauna as a whole not characteristic of the underlying beds, but the 

 arenaceous character of the deposit immediately below makes this 

 hypothesis untenable. 



These deposits must have resulted from a local depression, which 

 carried the sea-floor temporarily beyond the area of mechanical 

 deposition, and opened a communicating channel with the deeper sea 

 that still existed on the south or west. The limited area now 

 occupied by the limestone deposit near Botany would seem to point 

 to the west as the direction whence this fauna migrated : since, in 

 that direction, denudation has removed all the upper beds of the 

 Dibunopliyllmn Zone, and also the Millstone Grit; and so there is 

 nothing to prevent the deposit now described from having previously 

 extended in that direction. On the north-west and south, on the 

 other hand, there is a continuous upward sequence into the Coal 

 Measures ; but no limestones representing these beds occur else- 

 where in Durham or Yorkshire north of the Craven Faults. On 



