12 



ME. F. W. HARMER ON THE CRAG OF ESSEX. [NOV. I9OO, 



but fig. 2 (p. 711) represents a portion of it exposed at two localities, 

 at no great distance apart, the succession of beds being the same at 

 each. 



The upper part of the Crag now shown at this place is of a grey 

 colour, and is horizontally stratified ; while the lower part is ferru- 

 ginous, and obliquely-bedded at an angle of about 30°, the laminae 

 dipping south-south-westward. This oblique bedding was noticed 

 by Searles V. "Wood, Jun. at Walton and elsewhere thirty-six years 

 ago, 1 and it has, I think, an important bearing on the question of the 

 conditions under which the Red Crag originated. An unstratified 

 shell-bed, described by him in the same paper as resting upon the 

 London Clay, with the remains of mollusca in an undisturbed 

 position of growth, is not now visible. 



The upper part of the cliff-section is occupied by a bed of sandy 

 gravel, made up chiefly of flint, but containing also pebbles of various 

 kinds of quartz (pink and white), and of chert. This is underlain 

 by a band of grey sandy clay, which has been considered as possibly 

 of Chillesford age. 2 The clay and the gravel are, however, more or 

 less conformable one to the other and to the underlying Crag, and I 

 am inclined to think that both of the former may be of lied Crag age. 

 This view has been recently confirmed by my friend Mr. Lomas, 

 who has discovered that the sandy portion of the gravel is identical 

 in composition with that of the Crag. 



From Walton southward the cliff is composed of London Clay, 

 with a few obscure traces of gravel over it ; between Little Holland 

 and Clacton-on-Sea similar pebbly beds occur in the coast-section, 

 but in much greater thickness than at Walton, extending for 3 miles 

 or more to the north of Clacton (see map, fig. 3, p. 714). I suggest 

 that these gravels may be either fluviatile or estuarine, brought 

 down by a river which ran from the south-west at some period 

 later than that of the deposition of the Walton shell-bed, when the 

 southern margin of the Crag sea had retreated northward. 3 



The species of mollusca which I consider most characteristic of 



the Walton Crag are as follows 



Cypraa a veil an a. 



europaa. 



Valuta Lamberti. 

 Columbdla sulcata. 

 Nassa lakiosa. 

 pro pi n qua. 



granulata. 



reticulata and varieties. 



Buccinopsis Dalei 



Buccimim undatum. 



Purpura lapillus var. intermedia. 



■ tetragona var. alveolata. 



Trophon (Neptunea) cordrarius. 



( ) costijer. 



(Sipho) gracilis. 



( ) Olavii. 



( ) muricatus. 



Pleurotoma mitrula. 

 Cerithium tricinctum. 

 Turrit ell a incrassata. 

 Lacuna subaperta. 

 Natica catenoides. 

 hemiclausa. 



Trochus cineroides. 



1 Ann. & Mag. Nat. Hist. ser. 3, vol. xiii (1864). 



2 See Mem. Geol. Surv. (1877) 'Eastern End of Essex (Walton-on tbe-Naze 

 & Harwich)' p. 13. 



3 If this view be correct, the clay -bed is not of Chillesford age. 



