470 
DR. MANTELL ON FOSSIL FORAMINIFERA. 
Description of the Plate. 
PLATE XXL 
The specimens are represented as seen by transmitted light under the microscope, 
with the exception of figs. 13 and 15, which were viewed as opaque objects. The size 
of the originals is from about -^th to -^oth of a line in linear dimensions ; they are 
figured as seen by daylight ; when viewed by the illumination of a lamp, they appear 
more transparent, and of a lighter colour. 
Fig. 1. A Xanthidium from the grey chalk of Folk stone, presenting a torn and 
shrivelled appearance. 
Figs. 2 and 3. Specimens of mutilated Rotalise from the Folkstone chalk. 
Fig. 4. A single membranous empty sac of a Rotalia, very transparent. 
Fig. 5. The soft parts of a Rotalia from chalk ; the cells are distended with a dark 
substance. 
a, a, a-, globular bodies, probably ova. 
Fig. 6. The usual appearance of the shells of Rotalise in chalk, when mounted in 
Canada balsam : the interior is filled with chalk, and presents no traces 
of the animal matter ; numerous foramina are apparent. The shell of 
the specimen, fig. 10, was probably a larger individual of this species: 
from Dover. 
Fig. 7- The body of a Rotalia uncoiled, the membranous sacs and their connect- 
ing tube being extended : from Folkstone chalk. 
Fig. 8. A Rotalia in flint, with the internal parts preserved. All the chambers 
are occupied by the stomachs or digestive sacs, which are connected by 
the intestinal canal, and contain a brown granular substance. 
Fig. 9. The body of a Rotalia from the grey chalk of Folkstone, seen by trans- 
mitted light, and magnified 150 diameters. The shell and surrounding 
chalk have been removed by weak hydrochloric acid, and the specimen 
rendered translucent by immersion in Canada balsam ; by Mr. Deane. 
Fig. 10. The internal parts of a Rotalia from the chalk. The folds and duplica- 
tures of the integument of the digestive organs are beautifully displayed ; 
the intestinal canal is concealed by the membranous sacs ; the discoidal 
arrangement of these organs is preserved in the inner convolutions. This 
specimen is in an extraordinary state of preservation : from Folkstone. 
The original is about -^th of a line in diameter. 
Fig. 1 1 . Four large membranous sacs of a Rotalia seen in a fore-shortened position; 
the sacs are folded and collapsed. There are upwards of twenty ova (?) 
{a, a, a,) in connection with the anterior part of the specimen. 
Fig. 12. A Rotalia in flint, with the soft parts remaining in the shell; the sacs 
