LITTORINIDZ. 333 
“Cet animal ne laisse pas trainer la coquille comme le font 
les Cerites et la plupart des coquilles longues; il la reléve 
sous un angle assez aigu, la supporte sur un long pédicule, 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 Cecum, will, I think, go far to 
establish these genera as aberrant and modified developments 
of the Vermetide, and as a transition form from the Trochi 
to the Peloride of our method. 
The shell is smgular 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 pomts it 
may be observed, that I have not relied on the coimcidence of 
Vermetus, Cecum 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. 
LITTORINID. 
The following observations by us on this family were pub- 
lished in the ‘ Annals of Natural History’ at four different 
