J. S. GAELNEE ON" THE LOWER LONDOX TEETLAEIES. 205 



horizon can have crept in. Of 57 specifically determined bivalves of 

 the Thanet Sands, 13 pass into the so-called marine division of the 

 "Woolwich-and-Reading Beds, while of 12 bivalves from the latter, 

 only two, Cardium Laytoni, 31orr., and Teredo antenautce, Sby., do 

 not pass down into the Thanet Beds. If the Survey list is accurate, 

 there is thus no marked palaeontological break in the marine series. 

 There is equally no perceptible difference at Eeculvers in the quan- 

 tity of green grains in the two sets of beds ; while at Pegwell Bay a 

 layer of black flint pebbles occurs in what is acknowledged to be 

 Thanet Sands*. 



On these grounds I think the supposed break at this point, 

 the obscurity and difficulty in detecting which has been remarked 

 upon by all authors % should be ignored, and the succeeding 20 feet of 

 beds be regarded as an integral part of the same marine formation. 



Going back to where the Corhida-bed first rises, we see it ovei- 

 lain by about 8 feet of pale clayey sand mottled rust-colour, then 

 about 10 feet of grey mottled sand, 6 feet of fine orange-coloured 

 sand, 3 feet pale greenish sand mottled with orange, and a foot or so 

 of darker sand immediately under the Oldhaven pebble-bed. The 

 arrangement is slightly varied at the small chine already mentioned 

 (fig. 6), while at Oldhaven Gap (fig. 3) the succession is as follows : — 

 12 feet pale greenish- grey sand mottled with yellow and white ; 4 feet 

 6 in. slightly more clayey sand with ferruginous stains ; 7 inches 

 mottled grey and greenish sand giving an olive streak when cut ; 

 4 feet greenish sandy clay mottled in two shades, and with a few 

 small clay galls ; and 3 feet rusty brown sand mottled with greenish 

 yellow resting on the Corbida-'hed.. These beds are of comparatively 

 little interest, as the few fossils they contain are not of a distinctive 

 character. Iron pyrites, small lignitic fragments, and a few sharks' 

 teeth are found in them. They have apparently been mud-banks in 

 shallow water ; and the pyrites may be due to decomposed sea-weed. 

 A well-marked break occurs here, separating the next series. 



The Oldhaven Beds. 



These beds are rather sharply separated from the underlying beds 

 by a layer of black pebbles, sometimes 18 inches in thickness. 

 They are almost wholly composed of fine quartzose sand, with occa- 

 sional small lenticular patches of brown clay. Their distinctive cha- 

 racter is doubtless due to the fact that whilst the lower beds were 

 deposited under water, these were deposited between high- and low- 

 water marks by surf. They are seen first at the top of the cliffs west 

 of the point, and at the small chine (fig. 6) are about 36 feet above 

 the beach. The pebble-bed is here very distinct, some of the pebbles 

 being of large size, and all except the smallest perfectly rounded. 

 The top line is level as if smoothed by the waves ; but the lower line 

 is uneven. The pebbles are imbedded in loose sand, overlain by two 



* The Pegwell deposits seem to have occurred nearer shore, as indicated by 

 the presence of pebbles and broken-shell layers. 



t E. g. Whitaker, Quart. Journ. Geol. Soc. vol. xxii. pp. 409, 410, 419. 



