LITTORINIDjE. 333 



" Get animal ne laisse pas trainer la coquille comme le font 

 les Cerites et la plupart des coquilles longues; il la releve 

 sous un angle assez aigu, la supporte sur un long pedicule, et 

 s'avance dans une posture peu ordinaire aux mollusques." 

 Though these gentlemen describe a limited and peculiar pro- 

 gression, we have failed to discover one in the British species ; 

 I must therefore, for the present, presume that they have 

 scarcely the power of motion, and though perhaps not bodily 

 fixed, as in Vermetus, they are virtually so. They are always 

 found in great abundance in a tenacious mud, mixed with 

 shelly debris, that forms zones running between and amidst 

 the deepest waters of the coralline districts, in which I believe 

 they live buried and fixed, and can only protrude the head 

 and tentacula from the mass. These are strong and signifi- 

 cant facts, tending to prove the close connection of Turritella 

 and Vermetus, and, if considered with all that are mentioned 

 above, and those concerning Caecum, will, I think, go far to 

 establish these genera as aberrant and modified developments 

 of the Vermetidte, and as a transition form from the Trochi 

 to the Peloridte of our method. 



The shell is singular in not having longitudinal ribs or 

 varices, and in this respect is, I believe, only resembled by the 

 Aclis ascaris and Murex teres. There is scarcely the rudiment 

 of a canal in the aperture, but there are evident marks in all the 

 volutions of successive sinuations in the outer lip, that do not 

 amount to an emargination. In mentioning these points it 

 may be observed, that I have not relied on the coincidence of 

 Vermetus, Ceecum and Turritella withdrawing periodically 

 from the terminal volutions and plugging them up, as I be- 

 lieve all the turreted, elongated, slender species have that 

 faculty given them for the protection of the posterior part of 

 the body. 



LITTOBINID.E. 



The following observations by us on this family were pub- 

 lished in the ' Annals of Natural History ' at four different 



