Foraminifera of the Gault of Folkestone. By F. Chapman. 7 
and the greater width across the test. The latter point is perhaps 
the most constant character, and is 1 * 3 if the width of C. rotulata is 
taken as a unit. The central boss is usually large and transparent. 
It is very probable that, under the interpretation of the duality of 
form or dimorphism in the Foraminifera, we have here the micro- 
spheric C. rotulata and the megalospheric C. rotulata var. macrodiscus 
representing one species. 
This variety appears to be nearly as well distributed through the 
Gault as the type form. It has been recorded from the Upper Hils- 
clay and the Tardefurcatus- clay of North Germany (Reuss) ; and from 
the Gault of Montcley, Wissant, and 1’Aube (Berthelin) ; also from 
the Red Chalk of Speeton (as C. rotulata by Burrows, Sherborn, and 
Bailey). 
C. rotulata var. macrodiscus was found in the Folkestone Gault in 
zone ii., spec, h, very rare ; zone ii., spec, c., frequent ; zone iii., very 
rare ; zone iv., rare ; zone v., rare ; zone vi., rare ; zone vii., very 
rare; zone x., very rare; zone xi., 50 ft. from the top, rare ; 45 ft., 
frequent; 40 ft., rare; 35 ft., rare; 30 ft., rare; 25 ft., frequent; 
20 ft., rare; 12 ft., frequent; 6 ft., rare. 
Cristellaria gaultina Berthelin, plate I. figs. 10 a, h, 11. 
C. gaultina Berthelin, 1880, Mem. Soc. geol. France, ser. 3, vol. 1 
No. 5, p. 49, pi. iii. figs. 15-19. C. cultrata Burrows, Sherborn, and 
Bailey, 1890, Journ. Roy. Micr. Soc., p. 559, pi. x. fig. 18 a , h. 
This species is one of the commonest in the Gault series, and is 
very distinct in its characters. It is easily recognised by the rapid 
increase in size of the last chambers, which gives a sub-oval outline to 
the test ; by the produced extremity of the last chamber, and by the 
compressed form of the test seen in edge view. C. gaultina , more 
than any other Cristellarian from the Gault, shows a tendency in 
well-grown individuals to take on a wild irregular growth ; an example 
of this is given in plate I. fig. 11. In this particular specimen, the 
earlier and normal portion of the test (comparing it with other well- 
grown individuals), differs from the later portion, and it is evident 
that the plan of growth was subsequently somewhat changed after the 
fracture of the fragile apical extremity of the typical part of the test. 
It appears as if a resuscitation of life for the creature ensued by the 
accidental adherence of a growing fragment of another form to its 
broken oral apex. This aberrant mode of growth is also seen in 
other species occurring in the Gault. 
C. gaultina was originally recorded from the Gault of Montcley, 
A Tssant, and l’Aube (Berthelin), and under the name of C. cultrata 
has been figured from the Red Chalk of Speeton (Burrows, Sherborn, 
and Bailey). 
This species was found in the Gault of Folkestone in zone i., 
specimen a , very rare ; zone i., specimen h , frequent ; zone ii., speci- 
