Mr. W. Clark on the Animal of Dentalium Tarentinum. 323 
orifice: from the foot an elastic fibrous ribbon runs, on each 
side of the body, to the posterior terminus, and affords the ani- 
mal the power of greatly contracting and dilating that end of it, 
as may be seen by the creases of contraction, which in some 
degree give the appearance of annulations. 
At the base, and above the pedicle of the foot, if that surface 
of the animal is upwards which lies in the concavity of the shell, 
and vice versd, in the conyexity, is inserted a distinct light yel- 
low tubular buccal appendage, without eyes or tentacula, which 
can only be considered a kind of external cesophagus, and as re- 
gards its accessories and form, has no pretensions to be styled a 
head ; it is encircled by about eight or ten short dendroid ten- 
tacular strands ; its cavity forms two extremely dilatable pouches 
divided by a longitudinal septum, which become compressed 
and merge apparently into one at the pot of passage into the 
stomach ; these external receptacles invariably contain from ten 
to forty, or even more, very minute Foraminifera, a convincing 
proof of the voracity of these animals. I have never failed to find 
in them either the Quinque-, Tri-, or Biloculine, or the Rotalia 
Beccaru, the Lobatula vulgaris, Bulimina pulchella, Textularia 
oblonga, Lagena amphora, ov the Robulina subcultrata, and more 
rarely a minute bivalve, either the Kellia suborbicularis or Astarte 
triangularis: this fact is another proof, if any additional ones 
were necessary, that an animal inhabits the minute calcareous 
forms which were formerly supposed to inclose Cephalopoda, or 
to be inserted in their membranes ; they are not inhabitants of 
the littoral, but of the coralline zones, and appear to be the sole 
aliment of this decided zoophagous molluscum. These shells are 
an transitu to be acted on by the appendage within the stomach, 
which will be noticed shortly, and after having undergone its 
action the rejectamenta are discharged anteriorly with other 
mucal and fecal matters, and not at the posterior terminus 
agreeably to M. Deshayes’s determination, and I shall presently 
demonstrate that the posterior aperture is not for anal uses, but 
to supply the branchize with water. 
It is now necessary to mention the figure and situation of the 
heart and branchiz ; these points must be carefully kept in mind, 
as the demonstration I propose rests on a due consideration of 
them. The heart is a subrotund minute ventricle with a linear 
depression on its summit, and when opened shows the corre- 
sponding ridge ; its surface is fortified with muscular raised lines ; 
it is fixed centrally on the convex range at the posterior end of 
the branchial cavity and base of the stomach, and in some trans- 
parent animals may be seen in the pericardium ; in the very 
young pellucid shells seven inspirations and as many nearly 
isochronal expirations have been counted in a minute, and the 
22% 
