322 Mr. W. Clark on the Animal of Dentalium Tarentinum. 
between the animals of the two genera. I believe, with the ex- 
ception of M. Deshayes’s monograph, nothing has been done to 
elucidate this curious molluscum ; and as I think that eminent 
malacologist has mistaken the uses of some of its organs, I am 
induced, by the facility of obtaming live specimens of the Den- 
talium Tarentinum, to review and augment what is at present 
known of it: the present species inhabits the coralline zones of 
the South Devon coasts, five or six miles from land, in twelve or 
fifteen fathoms water. 
Dentalium striatum, Montagu. 
— Tarentinum, Lamarck. 
Animal yellowish white, conically elongated, mantle circular, 
anteriorly thick and fleshy, edge dentated, posteriorly of the 
thinnest texture ; the penultimate and antepenultimate portions 
of its margin are bounded by two intense white muscular elastic 
cordons ; the united action of these has the power of completely 
opening and closing the anterior aperture; when at rest, the 
animal, including the foot, is entirely inclosed by the tougher 
part of the mantle which supplies the place of an operculum. 
The foot is a very long and singular organ, placed in the cen- 
tre of the anterior end of the body, and from its position is ap- 
plicable for use in every direction ; it is divided into three parts: 
the anterior one is a pointed cone acting in some measure as a 
tentaculum, and lies in the middle portion, which consists of two 
lateral, simuated, symmetrical flaps or tenacula, that are usually 
protruded simultaneously with the terminal portion, and are the 
parts subservient to the animal’s very confined locomotion, to 
turn from side to side by using the lateral appendages as points 
d’appui, and also to climb and secure its food from the stems 
of the foraminiferous polyparia; the third or basal section is a 
long flattish pedicle deeply grooved on its upper and lower sur- 
faces, extending to the base “of the stomach, into which it opens, 
as it is hollowed out as far as the tenacular flaps, but there is no 
passage to the exterior surface. I have failed to discover the 
reason for this connection with the stomach: the hollow part is 
filled with water, but from what source does not appear, though 
I think it must come from the buccal aperture ; the use of this 
singular structure is clearly to augment the flexibility of the 
foot, as the animal frequently and suddenly doubles it up as the 
elephant does its trunk ; and also to withdraw the two anterior 
parts into the hollow portion : this retractile action is necessary 
im consequence of the peculiar mouth of the animal and rigid 
character of the anterior end of the mantle, to convey the sus- 
tentation captured by the tenacula into the cavity of the mantle 
within the reach of the very short foliaceous cirrhi at the buccal 
