44 REPORT — 1844. 



freshwater origin, and which are succeeded by a series of freshwater beds of various 

 mineral characters, in the midst of which a thin stratum of marine or brackish origin 

 suddenly appears. The measurements of all the strata, both tertiary and cretaceous, 

 and tables of their fossil contents, were laid before the meeting. 



Reviewing the strata deposited from the cessation of the Wealden to the prevalence 

 of a freshwater eocene formation in this locality, the authors laid stress on the follow- 

 ing facts in the local history of organised nature during that long period : — 1. That 

 the seas in which the lower greensand was deposited, and which occupied the area 

 described, in consequence of the sudden subsidence of the great Wealden lakes, pre- 

 sented from the very commencement a fauna truly marine, and most of the members of 

 which began their existence with the commencement of the cretaceous sera in England. 

 Almost all the animals which appeared were such as were new to the oceanic fauna ; 

 and among them were many forms representative of other species which had existed 

 in the oolitic ocean. 2. That this fauna continued, though apparently diminishing in 

 consequence of extinction of species from physical causes, until the commencement of 

 the deposition of the gault, when a new series of animals commenced, among which a 

 few species which had previously existed lived on, but the gi-eater part of which were 

 either representative or peculiar forms. The same system of animal life appears to 

 have continued throughout the remainder of the cretaceous aera in this locality, al- 

 though great differences in the distribution of species and many species local in time 

 occur, depending on the very great change in the mineral conditions of the sea-bottom 

 during this epoch. The chalks proper present especially many peculiar species, but 

 these appear rather to owe their presence to the zone of depth in which they lived, 

 than to being members of a new zoological representation in time. The authors called 

 attention to the assemblage of minute corals, sea-urchins, Terebratulae, and Spondylus 

 spinosus, in that part of the Culver section at which is seen the junction of the chalk 

 with flints and the hard chalk, as especially indicative of a very deep sea, and as 

 corresponding to the characters which mark a very deep sea fauna at the present 

 period. 3. That in the tertiary formations which succeed there is an entirely new 

 fauna, distinct as to every species in this locality, though elsewhere linked with the 

 cretaceous strata last alluded to by the presence of that remarkable mollusk, the Tere- 

 bratula caput-serpentis, which lives even at the present day. Of this fauna, which 

 did not appear imtil after a considerable bed of mottled clays, without traces of animal 

 life, had been deposited, the commencement is similar to the commencement of the 

 faunas of the two cretaceous periods already described; viz. by a series of clays con- 

 taining numerous peculiar Mya-form shells, Pectunculi, Ostrece, and their associates. 

 The earliest fossiliferous bed at Whiteclift^ bay is a most remarkable one, consisting of 

 a thin stratum almost entirely composed of a species of shell-bearing annelid, the 

 Ditrupa {DentaUum planum of Min. Conch.), which appears to have lived but a short 

 specific life in time, and to have suddenly disappeared. In the midst of these beds, 

 strata charged with myriads of foraminifera, probably indicating some change in the 

 sea's depth, appear and cease. The sudden conversion of the sea into a freshwater 

 lake, indicated by a stratum of paludina clay, its return into a brackish state, and the 

 consequent re-appearance of certain marine animals, its re-conversion into a fresh- 

 water lake thronged with myriads of fluviatile moUusca, and the almost momentary 

 influx of salt water during that period, which lasted only long enough for a race of 

 oysters to live and die away, — all render the tertiary strata in this locality highly 

 interesting. 



From the great zoological break between the eocene and the chalk, the authors 

 conclude that a third or uppermost cretaceous formation, characterised by a fauna 

 which would link the middle term of the system with the lowest term of the tertiary, 

 has disappeared in this locality; whilst they regard the portion of the cretaceous 

 system there present as composed of two divisions, equivalent in time ; the older con- 

 sisting of the lower greensand, and the upper, or later, forming one system, composed 

 of the gault, upper greensand, and chalks. 



The zoological epochs exhibited in the section, commented on and modelled, are there- 

 fore three, viz. — 1, the lower cretaceous system ; 2, the middle cretaceous system ; and, 

 3, the lower or eocene tertiary system. 



Critical Remarks on certain Passages in Dr. Buckland's Bridgewater 

 Treatise. By the Very Rev. the Dean of York. 



