C. E. De Ranee — Deposition of Cretaceous Strata, 251 



proposition, that the time will come when two distinct but parallel 

 classifications for dissimilar strata will have to be made, from the 

 breaks in the terrestrial and fluviatile fauna not corresponding to 

 those in the marine. Thus in the beds of Punfield Cove, Swanage Bay, 

 lying immediately above the Wealden, occurs a fluvio-marine fauna, 

 the marine contents of which Mr. Judd has shown are Neocomian, 

 while its fluviatile affinities are with the Wealden. And, again, 

 with the fluvio-marine beds of the Purbecks beneath, the marine 

 affinities are with the Oolites below, while the freshwater and ter- 

 restrial are Wealden, as shown by Prof Forbes, who in 1850 

 recognized the Neocomian facies of the fine collection of marine 

 fossils made by Mr. Godwin-Austen, F.E.S., at Punfield, and pre- 

 sented to the Geological Society. This " Punfield formation " shows 

 the strongest palseontological affinity to the middle portion of the 

 middle Neocomian Coal-field of Utrillas,' and other places in Eastern 

 Spain, wbere three Coal-basins occur, which it is believed will supply 

 " the whole of the peninsula for more than 200 years." 



The researches of M. Lory have shown that the Bhodanien of M. 

 Eenevier is as closely related to the Upper Neocomian (Aptien of 

 D'Orbigny) as it is to the Middle Neocomian (JJrgonien of D'Orbigny, 

 white limestone with Budistes). This proves, as pointed out by Mr. 

 Judd, the arbitrary division of tlie Upper and Middle Neocomian. And 

 when we see a marine fauna of upper Middle Neocomian age almost 

 intercalated in the upper part of the Wealden, and the equivalents of 

 a formation occurring in Spain more than oOO feet in thickness asso- 

 ciated with large and numerous coal and lignite beds, it is difficult to 

 resist his conclusion, that "as no break has ever been shown to exist 

 in the succession of Wealden beds in the south of England, we are com- 

 pelled to conclude that they represent the whole of the vast interval 

 between the Upper Oolite and the Upper Neocomian, Between the 

 Purbecks and the Portland Oolite the change is equally gradual, for 

 Mr. Godwin-Austen shows that the Swindon Purbecks absolutely 

 alternate with beds containing a Portland fauna. Just as in more 

 recent times, sections occur at the edge of the great belt of blown 

 sand surrounding the Lancashire coast The sand resting on the great 

 peat plain contains seams of peat with freshwater shells, alternating 

 with bands of sand, which become thicker and thicker in the upper 

 parts of the sections, the sand having gradually silted up the peat 

 morass, and the freshwater shells being replaced by rolled and wind- 

 worn sea-shells. 



Everywhere, indeed, in the geological formations, a change of 

 sediment appears to have brought a change of fauna, and in most 

 cases a recurrence of physical conditions induced a return of the old 

 fauna. In these cases it is clear that the change of sediment, and 

 of other physical conditions, depth of sea, climate of air, and temper- 

 ature of water, must have been local, though possibly extending over 

 large areas, and that extinction of species could only have taken 



^ The total thickness of the lignite and coal series, consisting of the Upper and 

 Middle Neocomian lying beneath the Gault, is given by Mr. Judd at 1600 feet. 



