192 Mr. Mowracv’s Account of some new and rare 
destitute of locomotion, and is immovably fixed from its earliest 
infancy to whatever chance has thrown in its way: to this sub- — 
stance, be what it may, it throws out from the perforation in the 
under valve a ligamentous pedicle or foot, which becomes firmly 
attached ; and in the course of time, as the animal grows, a testa- 
ceous plug is formed on the object of its adhesion, and as firmly : 
connected to a rock or other substance, as it is to the pedicle or 
part which has secreted the testaceous fluid ; and no separation 
can ever take place without external violence and consequent mu- 
 tilation. On the contrary, if we attend to the habits of T. Cranium, 
Vitrea, or any of those Linnean Anomie with a perforation in the 
beak of the upper valve, I am persuaded that we shall find all of 
them to be inhabited by animals capable of a certain degree of 
locomotion ; and that, instead of being moored fast for life by a 
pedicle issuing from the perforated valve, these animals receive 
all their nourishment through this aperture by means of a tubular 
mouth, which has also the property of adhesion when required, 
either for the purpose of securing them stationary, or to acquire 
locomotion by extension and contraction, as I have observed in 
the animal of Mya suborbicularis, and one or two others, which - 
appear to be inbabited by a Tethys. 
From what has been related, it may naturally be imagined 
that the internal structure of the shells in question must mate- 
rially differ, and such'is actually the case, without the excep- 
tion of one solitary character; but this I shall not here enlarge 
upon, as a comparison is readily obtained by the scientific 
Conchologist. een | 
- Lamanon, as well as some other French naturalists, have consi- 
dered some shells similar to this, perfectly distinct from Anomia T 
and that very judicious physiologist Muller has separated them, 
and has adopted the generic title of Terebratula for those of 
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