Mr. W. Clark on the Animal o/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 versa, in the convexity, is inserted a distinct light yel- 

 low tubular buccal appendage, without eyes or tentacula, which 

 can only be considered a kind of external oesophagus, 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 point 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 Biloculina, or the Rotalia 

 Beccarii, the Lobatula vulgaris, Bulimina pulchella, Teoctularia 

 oblonga, Lagena amphora, or 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 

 in 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 faecal 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 branchiae with water. 



It is now necessary to mention the figure and situation of the 

 heart and branchiae ; 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 



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