W. W. Watts — British Geological Photographs. 109 



Pterinea Mortensis and Modiolopsis Barricanensis, do not, in any way, 

 bear out the statements in regard to measurements which he gives, 

 if the distortion by cleavage be taken into account. P. Mortensis is 

 greatly reduced in length, and increased in width by pressure, 

 so altering the whole shape of the shell and wings. In its normal 

 condition it would agree well with some Pterinece from the Silurian. 

 Some paljBontologists have thought that it might be closely allied to 

 Avtcula Danhiji, a well-known Silurian form (see figs, of A. Banhyi 

 in McCoy's " British PalEeozoic Fossils "). The distinction between 

 Modiolopsis and Modiomorpha rests in the dentition, but unfortunately 

 this cannot be seen in any of the specimens hitherto found. None 

 of the statements made by Dr. Gregory can therefore in any way 

 affect the evidence, stratigraphical and palseontological-, which I have 

 brought forward to show that the Morte Slates are the oldest rocks 

 in North Devon. 



III. — Notes on British Geological Photographs. 

 By W. W. Watts, M.A., F.G.S. 



[Concluded from the February Number, p. 62.) 



(PLATES III AND IV.) 



S promised last month, we now add a brief note on Plates III 

 and IV of this series, given in this number. 



Plate III is one of a beautiful set prepared by Mr. Godfrey 

 Bingley for insertion in the Proceedings of the Yorkshire 

 Geological and Polytechnic Society, from which the plate is 

 borrowed by the kind permission of the editor, the Eev. W. L. 

 Carter. A full description by Mr. G. W. Lamplugh. will shortly 

 appear in the " Proceedings " of that Society, and from the 

 manusci'ipt of this I have been permitted to extract the following : — 



The cliff to the left is the most easterly point of Flamborough 

 Head ; it is formed of the lowermost beds of the flintless Upper 

 Chalk, resting on the uppermost beds of the flinty Middle Chalk, 

 which are seen just above sea-level. In the Chalk a steep-sided 

 valley has been eroded which is now filled with drift. One bank 

 of this valley is to be seen in the exact middle of the picture just 

 above sea-level ; the rocky bottom of it runs away to the right, and 

 the drifts in it occupy the whole right-hand half of the photograph. 

 First comes chalk rubble, then boulder-clay, next a seam of dark 

 gravel, seen projecting out of the dark shadow thrown by the sharp 

 ridge to the right, then a light gravel with lumps of chalk, and 

 lastly, extending to the relic of the plateau at the top. Upper 

 Boulder-clay. The characteristic weathering of the drift is shown 

 by the ridges and knife-edges, and the great crater or blow-hole 

 which is such a conspicuous feature in the photograph results from 

 the tapping of the old valley by a small cave driven through its 

 wall ; this cave is just out of sight in the shadow of the overhanging 

 cliff in the middle of the picture. 



Plate IV is taken from a beautiful panoramic view by Mr. E. J. 

 Garwood, and published by him in the " County History of 



