Geology. 21 



layers, which are very variable in extent and thickness, is banked 

 up against an old river-cliff consisting of Chalk and Tertiary beds. 

 In places the shells from these older formations, and large blocks 

 from indurated beds in them, occur as derived specimens in the 

 Brickearth. Messrs. A. L. Leach and R. H. Chandler have recently 

 studied these beds in detail for a considerable time, and the re- 

 marks following are mainly from their notes (18). The well-known 

 CORBICULA FLUMINALIS band has been traced by them over a large 

 part of the Brickearth-area, but the shells are not always abundant. 

 Messrs. Hinton and Kennard regard the implements found in these 

 beds as of Mousterian type. 



The large old pit (Stoneham's) near Crayford, from which Prof. 

 Dawkins obtained the skull of OVIBOS MOSCHATUS, and Mr. F. C. J. 

 Spurrell discovered the Palaeolithic Floor, is now worked out. The 

 CORBICULA band can, however, still be well seen. 



At Rutter's Pit, on the western side of the road from Crayford to 

 Erith, and connected by a tunnel to a large pit on the eastern side, 

 a curious conglomerate has been found at the base of the Brick- 

 earth. It consists of rolled and unrolled flints, cemented together 

 by a calcareous concretion known as " race." Pebbles of quartz, 

 sandstone, and quartzite also occur in it. Many of the flints are 

 very dark, and one of these gave evidence of being worked. Many 

 bones of the larger Pleistocene Mammalia have been obtained from 

 the Brickearth. As recently as February 10th, 1907, Mr. Chandler 

 saw a portion of a tusk 5 inches in diameter, in addition to several 

 other large bones in place. 



The Corbicula-layer has yielded many fine specimens of COR- 

 BICULA FLUMINALIS, BYTHINIA, PlSIDIUM, PLANORBIS, HELIX, 



VALVATA, UNIO, and ANODONTA. CYPRIDS and CHARA have 

 also been detected above the tunnel in the eastern side of the road. 



Above the Brickearth is a contorted layer of gravel, brickearth, 

 etc., termed " trail." It is well shown in this pit, and has been 

 attributed to ice-action, and partly to ice-movement and partly to 

 rain-wash over frozen soil (19). 



At Norris's Pit, which lies nearer to Erith than Rutter's, on the 

 western side of the road, is another fine series of sections showing 

 the Brickearth cut back to the old river-cliff. The Brickearth in 

 places is crowded with remanie Tertiary shells, MELANIA, CERITHIUM, 

 and C YUEN A from the Woolwich and Reading Beds being plentiful. 

 Large blocks, too, of shelly conglomerate occur, probably derived 

 from the Blackheath Beds, which occur in place to the west. Some 



(18) Proc. Geol. Assoc., Vjl. XIX., p. 137, and Vol. XVIII., p. 165. 



(19) Proc. Geol. Assoc., Vol. XVIII. 



