ANNIVERSARY ADDRESS OF THE PRESIDENT. lui 



ful to which it should be referred. The fish in question had, as Sir 

 Phihp Egerton observes, a close resemblance to the Sciaenoids and 

 particularly to the genus Pristipomn, in the characters of the organs 

 of locomotion, and in the general form of the trunk ; but in the 

 opercular apparatus and osteology of the cranium, it more nearly 

 approaches the Percoids. The dentition differs from both, and re- 

 sembles that of some of the Sparoids. 



To the continued exertions of Mr. Prestwich we are indebted for 

 several papers containing much valuable detail respecting the Ter- 

 tiaries of the London and Hampshire basins. The first paper, on 

 the thickness of the London Clay, is full of information obtained 

 from the most authentic sources ; and the manner in which Mr. 

 Prestwich has tested and checked the information he received, is 

 deserving of the highest praise. The position and distribution of 

 the organic remains throughout the whole series are carefully given, 

 and the different zones in which they occur are well worked out. 

 The value of this portion of the paper has been materially enhanced 

 by the publication for the first time of the separate lists of fossils 

 contained in these different zones. The principal zones referred to 

 by Mr. Prestwich are, — 1 . Isle of Sheppey. 2. Ilighgate. 3. Prim- 

 rose Hill, Copenhagen Fields, Whetstone, Islington, Haverstock 

 Hill, Hornsey, Holloway, and Hampstead. 4. Bognor. It must 

 be borne in mind, however, that Mr. Prestwich restricts the term 

 "London Clay" to one of the lower deposits of London and of Hamp- 

 shire, excluding therefrom the Bracklesham and Barton beds. 



The next paper by Mr. Prestwich is on the distinctive physical 

 and palseontological features of the London Clay and Bracklesham 

 Sands, and on the independence of these two groups of strata. The 

 object of this paper is to confirm, chiefly on the evidence of the 

 organic remains, the opinion already pronounced by the author in a 

 former communication, that these two formations are not sjaichronous; 

 and to endeavour to disprove the opinions of other geologists, espe- 

 cially those on the continent, who have considered that the differences 

 in the characters of the fauna of these several beds v/ere dependent on 

 geographical distribution, depth of water, or variations of sediment. 

 The author points out the confusion which has arisen in the com- 

 parison of the London and Paris basins, in consequence of this di- 

 stinction not having been sufficiently attended to, and the characteristic 

 fossils of the London Clay proper and the Bracklesham Sands having 

 been grouped together as belonging to one formation. -After de- 

 scribing the different lithological characters of the two groups, Mr. 

 Prestwich enumerates the number of species of the different classes 

 of organic remains occurring in the two formations, and points out 

 how few species are common to both. Thus — 



Mammalia. . . 



London Clay. 

 2 .. . 



Bracklesham. 

 1 . . . 



Common, 

 . . . 



Birds 



4 . . . 



1 .. . 



. .. 



Reptiles . . . 



VOL, XI. 



21 . . . 



7 .. . 



. .. 2 







d 



