DR. MANTELL ON FOSSIL FORAMINIFERA. 
467 
shell is removed by weak hydrochloric acid, the soft body is exposed, and is seen to 
extend to the innermost chamber ; and there is a connecting tube occupying the 
place of the siphuncle of the Nautilus, but which is the intestinal canal; for the cells 
of the shell contain the receptacles of the digestive sacs or stomachs, in which 
minute Infusoria (as Monads, Naviculee, & c.), that have been swallowed by the animal, 
may sometimes be observed. 
In the fossils, the appearance of the parts which I suppose to be the digestive 
organs, is that of a series of bladders or sacs, composed of a tough, flexible skin or 
integument, connected by a tube. These organs are more or less filled with a dark 
substance ; those which are distended are always well-defined, while the empty ones 
are collapsed and disposed in folds, just as membranous pouches would appear under 
similar conditions. The sacs regularly diminish in size from the outer to the inner- 
most cell, and vary in number from fourteen to twenty-six ; being far more nume- 
rous than in the recent species. In some instances small papillae are observable on 
the external surface of the integument ; these are probably vestiges of the pseudo- 
podia or tentacula. 
The specimens to which I would first solicit attention are two Rotaliae in flint 
(figs. 8 and 12). In the example, fig. 12, which is seen in an oblique direction, the 
outline and thickness of the shell and its septa are distinctly visible ; as if a longitu- 
dinal section had been made through the shell, and the portion nearest the observer 
removed. Every compartment contains a brown granular substance, and the con- 
necting tube is partially distended with a similar material. In this specimen, either 
a portion of the shell has been removed by the section of the flint so as to display the 
internal parts, or it has been transmuted into silex so transparent as to elude obser- 
vation*. As an object of comparison with this fossil, the shell of a recent species 
from the Levant, seen by reflected light with a low power, is represented, fig. 15. 
The general contour of the shell is nearly the same in both ; but in the recent example 
the outer surface remains, and exhibits the characteristic foramina of the genus. In 
the chalk Rotalise the perforations are for the most part obscured by the calcareous 
investment ; but occasionally specimens both of the single and compound Polytha- 
lamia are met with, in which they are well-displayed ; and in some instances the 
foramina are filled by a dark material, as if the bases of the tentacula were remaining' 
in the state of molluskite-f-. 
The fossil, fig. 8, is contained in the same atom of flint as that above described. 
The interior of the animalcule is here completely exposed ; the sacs and the intes- 
tinal canal are as perfect as in an individual recently dead, and just taken out of the 
sea. The folds of the sacs that are but partially filled with the brown endochrome, 
* The Polythalamia •which occur in the chalk surrounding sponges inclosed in flint nodules, are frequently 
in a silicified state, and appear as transparent as glass, under the microscope. 
t the silicified Rotaliae the foramina are frequently well-displayed. 
3 p 2 
