Foraminifera of the Gault of Folkestone. By F. Chapman. 5 
of Cristellarians of which C. rotulata is the type, and differs from 
that form in the general elongation of the test in the direction of the 
oral extremity. C. gibba is in its general characters intermediate 
between C. rotulata and C. crepidula. Gradational examples are 
found which pass insensibly into C. planiuscula, but this latter form 
is in typical specimens strongly compressed. 
C. gibba has been recorded from strata as old as the Lias (Crick 
and Sherborn). As a Cretaceous form it has been found in the Upper 
llils-clay and the Speeton Clay of Brunswick (recorded as C. nuda by 
Beuss) ; from the Bpeeton Clay and the Minimus- clay of Germany 
(as C. pulchella by Beuss); and from the Chalk of JEtugen (as 
C. nuda by Beuss). In this country it has been noted from the 
Neocomian beds of Surrey (Chapman) ; * and from the Bed Chalk of 
Speeton (Burrows, Sherborn, and Bailey). 
The species has apparently not yet been noticed in Tertiary 
deposits, for we can scarcely include under this specific name C. 
excisa Bornemann,f which has been placed in the synonymy of the 
species in the Beport on the ‘ Challenger ’ Foraminifera.J 
At Folkestone the occurrences of C. gibba in the Gault were: — 
Zone i., spec, b., frequent ; zone iii., rare ; zone iv., very rare ; 
zone v., frequent ; zone vii., very rare ; zone viii., very rare ; zone x., 
rare; zone xi., 55 ft. from the top, rare'; 50 ft., rare; 45 ft., rare; 
40 ft., frequent ; 35 ft., rare ; 25 ft., rare; 12 ft., frequent ; 6 ft., 
rare. 
Cristellaria rotulata Lamark sp., plate I. fig. 8 a, b. 
Lenticulites rotulata Lamarck', 1801, Annales du Museum, vol. v. 
p. 188, No. 3 ; Tableau Encycl. et Meth., pi. cccclxvi. fig. 5. Cris- 
tellaria rotulata d’Orbigny, 1840, Mem. Soc. geol. France, ser. 1. 
vol. iv. p. 20, pi. ii. figs. 15-18. Bobulina Munsteri Bomer, 1811, 
Yerstein. norddeutsch. Kreidegeb., pt. 2, p. 98, pi. xv. fig. 30. Cristel- 
laria rotulata Beuss, 1846, Yerstein. bohm. Kreidef , pt. i. p. 34, pi. 
viii. figs. 50 a, b, 70. C. munsteri Beuss, 1862, Sitzungsb. d. k. Ak. 
Wiss. Wien, vol. xlvi. p. 77, pi. ix. figs. 3 a, b, 4 a } b. C. rotulata 
Brady, 1881, Chalk Bep., vol. ix. p. 547, pi. lxix. fig. 13 a, b. 
C. rotulata Perner, 1892, Foraminifery Ceskeho Cenomanu, p. 62, 
pi. iv. figs. 1-11. 
Among the Cristellarians from the Gault there are numerous 
varieties which, from a biological standpoint, should be relegated to 
the well-known cosmopolitan form C. rotidata. The examples from 
Cretaceous deposits have unfortunately been split up into innumerable 
so-called species, many of which have no claim to stand, even as 
varieties, on account of their close relationship and even identity with 
one another ; and this is especially evident when a large number of 
specimens are examined. 
* Quart. Joum. Geol. Soc., 1. (1894) p. 714. 
t Zeitschr. d. deutsch. geol. Gesell., vii. (1855) p. 328, pi. ii. figs. 19, 20. 
X Vol. ix. (1884) p. 546. 
