472 EH. Neaverson—Foraminifera of the Hartwell Clay. 
species, Cristellaria rotulata, C. gibba, and C. cultrata. A specimen 
of Vaginulina truncata and one of Haplophragmuum neocomianium 
connect the assemblage with the Lower Cretaceous. The only point 
of comparison with the Hartwell Clay is in the occurrence of the 
Cristellarians mentioned above. The Upper Jurassic of Switzerland 
has yielded arenaceous forms referred by Haeusler to Thurammina: 
albicans, and similar forms are occasionally found in the Hartwell 
Clay. 
Of the thirty-six species from the Hartwell Clay, thirteen (or 
36 per cent) are known from the Hils of Germany. The foraminiferal 
assemblages of the two deposits are connected by (1) the dominance 
of Cristellaria and Vaginulina, and (2) the comparative rarity of 
arenaceous forms. A notable difference is the presence of twelve 
species of Nodosaria in the Hils against four in the Hartwell Clay. 
Lagena is not represented in the Hils assemblage, but four species 
occur in the Hartwell Clay. 
The Foraminifera throw little light upon the question of the depth 
at which the Hartwell Clay was deposited. Nineteen of the thirty- 
six species are still living and eleven of these are recorded by Brady 
from both shallow and deep water. Of the eight species remaining, 
three, Thurammina albicans, T. papillata, and Cristellarva convergens, 
are characteristic of deep water, whilst five occur in shallow water. 
The balance of the evidence seems to be in favour of fairly deep 
water, since tests of shallow water. forms could sink to the level 
of deposition. The Hartwell Clay itself shows great similarity with 
the Gault Clay both in the abundance of glauconite and in the presence 
of certain species of Foraminifera. Thus it is permissible to 
suppose that the depth of deposition would be similar, viz. hetween 
800 and 900 fathoms according to Chapman’s calculation for the 
depth of the Gault Sea.t 
SUMMARY. 
1. Thirty-six species of Foraminifera are recorded from various 
localities in the Hartwell Clay and associated beds. 
2. The assemblage of species is characterized by :— 
(a) the abundance of rotulate Cristellarians of Lower 
Cretaceous type, and of Cristellaria fragraria. 
(b) the common occurrence of Vaginulina harpa, a Jurassic 
type. 
(c) the rarity of arenaceous, and the absence of porcellanous 
forms. 
3. The Foraminifera from the Hartwell Clay are compared with 
those from other deposits in the Aylesbury district, and with those 
from foreign deposits of similar age. 
4, The relative abundance of glauconite is a point of similarity 
between the Hartwell Clay and beds hitherto regarded as 
Kimmeridge Clay. 
1 Nat. Sct., vol. xii, 1898, No. 81, p. 305. 
