122 MESSES. JT7KES-BR0W1JE AND SCANES ON THE [Feb. I9OI, 



Popplestone-Bed is a clear line of separation from the sand below, 

 and the chief palaeontological break coincides with this line ; though, 

 again, this may be due to the rarity of fossils in the sand below. 

 Both here and at Maiden Bradley this sand contrasts markedly in 

 lithological character with the fine silts of the underlying Chert-Beds. 



We think that anyone who studies these sections by themselves 

 will come to the conclusion that the most natural plane of division, 

 so far as the local distribution of fossils is concerned, is at the base 

 of the Cornstone-Bed. But he will be compelled to admit that a 

 greater abundance of fossils in the sand below might oblige him to 

 place the division % few feet lower down ; and he must also admit 

 that there is a certain change of fauna where Stauronema Carteri 

 comes in. 



The close affinity between the so-called ' Warminster fauna ' and 

 that of the Chloritic Marl was perceived by the late C. J. A. Meyer 

 so long ago as 1874,^ when he expressed his belief that 



' the fossiliferous poi-tion of the so-called Upper Greensand of Warminster is, 

 properly speaking, Chloritic Marl instead of Upper Greensand, as usually 

 stated.' 



The many points of connexion between the two faunas were ad- 

 mitted by one of us in 1896, who remarked that ^ 



' if the Rye Hill Sand were only known as an outlying patch situated further 

 west, and we had only the evidence of the fossils to guide us in determining its 

 geologic age, it might hare been regarded as a shallow-water deposit of the age 

 of the Chalk-Marl, and the ammonites might have been appealed to as strong 

 evidence in support of the contention.' 



At the same time, this Rye Hill Sand was retained in the Upper 

 Greensand, and distinguished from the true Chloritic Marl because 

 the latter was found to lie above it. With this view Mr. Meyer 

 had previously signified his agreement in a joint note with the 

 same writer.^ 



If the evidence adduced in the present paper obliged us to re- 

 consider the above conclusion, and to regard the more fossiliferous 

 part of the E-ye Hill Sand as attached to the Chloritic Marl rather 

 than to the IJpper Greensand, it is evident that the fauna which 

 has been recorded from that sand would have to be transferred 

 from the Selbornian to the Cenomanian. 



It is here that the considerations mentioned on p. 120 come in ; 

 and consequently we must make some reference to other localities, 

 in order to see whether such a re-arrangement would not raise 

 more difficulties than it would solve. 



If we follow the beds from Southern Wiltshire into Northern 

 Dorset, we find a large area where there is a clear plane of demar- 

 cation between the Greensand and the Chalk. The topmost bed of 



^ Quart. Journ. Geol. Soc. vol. xxx, p. 381. 



2 Jukes-Browne in Geol. Mag. 1896, p. 272. 



3 See Geol. Mag. 1894, p. 495. 



