200 NATURAL SCIENCE [September 
Chalk (including the zone of Stauronema). Here also the true rela- 
tions of the fauna are quite clear. 
In this study of the fauna of the English zone of Am. rostratus 
I have excluded Echinoderms, because their evidence is not of first- 
rate value; in support of this opinion, I may quote that of Dr J. W. 
Gregory of the British Museum, who has remarked that, “Echinids are 
rather a clue to the conditions of formation of deposits than evidence 
of their exact contemporaneity in age.” Thus it may be quite true, 
as Mr Lambert declares, that the affinities of the Echinoidea found 
in the Gaize of Havre are Cenomanian, but their evidence cannot weigh 
against that of the Cephalopoda which are most clearly not Cenomanian. 
Mr Dollfus quite omits to notice that I have appealed to the 
Cephalopoda as affording the best criterion of the affinities of the 
fauna of these beds. Let us see what this criterion proves. 
From the Upper Gault of Folkestone Messrs Price and De Rance 
have recorded 31 species of Cephalopoda, and of these 12 range down 
into the Lower Gault, and only 4 range into beds above. Similarly 
in the Gaize of Devizes there are 20 Cephalopods, of which number 
7 occur in Lower Gault and 4 range into higher beds. Both at Folke- 
stone and Devizes Ammonites rostratus and A. varicosus are restricted 
to the Gaize and Upper Gault, but in the counties of Buckingham 
and Bedford, I have myself found both species in the Lower Gault. 
In two cases they were in company with A. Jautus and A. splendens 
about 30 feet from the base of the Gault which is there 200 feet 
thick ; in a third case they occurred with A. interruptus quite near 
the base of the Gault. With respect to the upward range of A. rostratus, 
it passes upward into the green glauconite sands above the Gaize, 
both in Wiltshire and Dorset, and where the Chert Beds are absent, 
I have found it within six or seven feet (two metres) of the top of 
the Upper Greensand. No Ammonites have yet been found in the 
Chert Beds, but A. rostratus has never been found above them. 
Next let us consider the true Cenomanian group of Cephalo- 
poda :—Ammonites varians, falcatus, mantelli, navicularis, rotoma- 
gensis, Scaphites aequalis, Turrilites costatus, tuberculatus. No one 
who has collected along the south coast of England or at Wissant, 
or at Havre, could doubt where these species first set in as common 
fossils; they come in with Stawronema carteri and A. laticlavius in 
what is generally called the Chloritic Marl. | 
It is only occasionally and locally that any of them occur below 
this horizon, but so far as my experience goes not one of them 
ranges further than six feet below it. A. varians, faleatus and 
navicularis are not uncommon at the top of the Greensand between 
Warminster and Maiden Bradley, but are not associated with A. 
rostratus ; the bed in which they occur is evidently a passage bed 
from Greensand to Chloritic Marl. 
