272 A. J. Jukes-Brotcne — 



No fewer than 13 of the species occur in the Chalk Marl, and it is 

 clear that there is a preponderating Chalk Marl element in the 

 Echinoid fauna of the Rye Hill Sand. The fact has been noted 

 before, though it has not been stated correctly ; thus, Dr. Wright, 

 in his Monograph on the Cretaceous Echinodermata, makes the 

 following remarks : " I have long noticed nearly all the Upper 

 Greensand Echinida3 are found in the Grey Chalk, and that the 

 specimens from the latter stratum are in general larger and more 

 fully developed, as if they had been better nourished, than those 

 collected from the arenaceous beds of the Upper Greensand of 

 Wiltshire and other localities." 



The mistake Dr. Wright and everyone else have made is in 

 regarding all these Warminster Echinoderms as characteristic 

 Upper Greensand species. They are really Chalk Marl species, 

 and the very topmost bed of the Greenland at Warminster and 

 elsewhere is, for many of them, the limit of their downward range. 

 In other words they are not Greensand species, but Chalk species 

 which make their first appearance at this horizon. 



Actinozoa. — Only four corals have been obtained from the Rye 

 Hill Sand, and three of these are Chalk forms, the fourth being 

 Astroccenia decaphylla, for which the only other known locality is 

 Haldon, in Devonshire, and as the coral bed there is at the top of the 

 Greensand it may not be older than the Rye Hill Sand. 



Reviewing the above pabeontological evidence, we find that the 

 total number of species which range up into the Chalk Marl is much 

 greater than the number of those which range down through the 

 Upper Greensand, and this is so after the exclusion of many species 

 which have hitherto been admitted as Warminster fossils, but which 

 really came from the Chloritic Marl. Roughly speaking and setting 

 aside those which range both ways, the species ranging upward are 

 nearly three times as many as those ranging downward. 



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 have 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. Nor would the conclusion have been 

 very far wrong, for the bed is only just below the Chalk Marl. 



This preponderance of upward-ranging species in the Rye Hill 

 Sand accounts for the idea put forward in 1874 by Mr. C. J. A. 

 Meyer 1 that "the fossiliferous portion of the so-called Upper 

 Greensand of Warminster is, properly speaking, 'Chloritic Marl,' 

 instead of 'Upper Greensand,' as usually stated." Judging from 

 the collections of Warminster fossils seen in museums, and without 

 the stratigi'aphical knowledge which has since been obtained, it was 

 a very natural conclusion on his part, though it is not strictly correct. 



The limitation of the so-called Warminster fauna to a few feet 

 at the top of the Upper Greensand has an important bearing on 

 the Cenomanian question, for it will show our French confreres 

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



