440 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 5, 



teristic of genera, — as, for instance, the keel, or dorsal, valve in Scal- 

 pellum, and the scutal, or inferior lateral, valve in PolUcipes. The 

 pedunculated cirrhipeds (Lepadidce) were stated to have made their 

 first appearance in the lower oolite, and to have reached their culmi- 

 nant point in the cretaceous epoch. The absence of sessile cirrhipeds 

 in the earlier and secondary formations, and their occurrence for the 

 first time in the eocene deposits, were then noticed, the author dwell- 

 ing on the characters of the genus Verruca, and pointing out that, as 

 the type of a group intermediate between, and of equal value with, 

 the sessile and the pedunculate cirrhipeds, it offered no real excep- 

 tion to the rule that sessile cirrhipeds do not occur in the secondary 

 foJ'mations ; but that, on the contrary, it harmonizes with the law 

 of relation between serial affinities of animals and their first appear- 

 ance on this earth. Mr. Darwin concluded with a few observations 

 on the comparative ranges of recent and fossil cirrhipeds, and on the 

 close affinities between the extiuct and the living forms. 



2. On the Tertiary Strata and their Dislocations in the 

 Neighbourhood of Blackheath. By the Rev. H. M. De la 

 CoNDAMiNE, M.xl., St. John's Coll., Camb. 



[Communicated by Sir H. T. De la Beche, V.P.G.S.] 



The cuttings of the North Kent Railway yielded some good sections of 

 the Plastic Clay series, and disclosed an important line of dislocation at 

 Deptford ; — important because a close approximation to its date can 

 be obtained, and because it has affected the present configuration of 

 the adjoining country. The abrupt escarpment of the chalk and 

 plastic clay along the south side of the Thames is manifestly due in 

 some measure to this dislocation, which also accounts for the presence 

 of the London clay under the Greenwich marshes at an unexpectedly 

 low level. 



Before proceeding to consider the effects of this dislocation, it will 

 be well to describe the strata which it has affected. And this de- 

 scription derives interest from the fact that these strata are perfectly 

 regular over a large extent of country ; their order of superposition 

 and organic contents being constant, and their mineral composition 

 exhibiting no great variation. Table I. shows the localities where 

 the succession of strata may be most advantageously studied ; and 

 Table II. the correspondence between the subdivisions existing in 

 this district and those observed elsewhere, and recorded by Mr. 

 Prestwich"^. 



* Quart, Joum. Geol. Soc. vol. ii. 



