10 Geology. 



The chalk of the zone of MICRASTER COR-ANGUINUM at Abbey 

 Wood, Wickham, Charlton, Westcombe Park, Keston, andDowne^ 

 contains beautiful fossils, which require a considerable amount of 

 patience on the part of the worker before he can be said to possess 

 a typical collection. The parts worked by the author at Westcombe 

 Park are now covered by rail wa,y- works. The fauna of the above 

 exposures is identical with that of Gravesend which marks the 

 upper part of the M. COR-ANGUINUM zone, containing the Belemnite 

 remains, ACTINOCAMAX VERUS and A. GRANULATUS. 



A few words respecting the flints may be of interest. At 

 Westcombe Park many of them are hollow and contain much 

 chalcedony. Occasionally beautiful nodules are met with having 

 stalactitic chalcedony. At Keston many of the nodules exhibit a 

 surface (always upon a fractured end) of minute mammillated 

 chalcedony, light-blue and arranged in an agatifonn manner. 

 At Cox's Mount the writer has taken from the chalk immediately 

 underlying the Thanet Sand green-coated casts of Echinoderms, 

 in an upright position, the test having been diesolved by the action 

 of water percolating through the overlying sand. 



Messrs. Leach, Polkinghorne and Chandler have paid great 

 attention to the Chalk at Wickham and Abbey Wood, and a list of 

 the fossils has been published in Proc. Geol. Assoc., vol. xix., 

 p. 345. In their report of an excursion here, Dr. Rowe gives it as his 

 opinion (in the absence of Micrasters) that, judging by the other 

 fossils, the Chalk belongs to the zone of M. COR-ANGTJINUM. Mr. 

 Leach, in a letter to the writer, says : "I have since found an 

 excellent specimen of the zone-fossil." The writer had obtained 

 one previously, though unknown to Mr. Leach, also an excellent 

 specimen of CONULUS ALBOGALERUS and other fossils that, in the 

 absence of UINTACRINUS and MARSUPITES, left no doubt in the 

 writer's mind as to the age of this Chalk. 



Unfortunately, nearly the whole of the Chalk in our district is 

 subterranean, and it is only from information given by deep 

 excavations, such as the present sewerage- works, that knowledge of 

 its distribution can be gained. 



4. EOCENE TERTIARIES. BY A. L. LEACH. 



/ 



Introductory Note. 



The district is practically encircled by the Drift-deposits of the 

 Thames, Cray and Ravensbourne, but within the area the older 

 Tertiary beds form nearly the whole surface. The London Clay 

 occupies perhaps a third of this surface, and the Blackheath pebble- 



