Mr. Say on the genus Ocythc&. 109 
With respect to the contested question relative to the 
parasitic nature of the animals of this genus, I believe the 
remark will hold good generally, if not absolutely, that those 
mulluscous animals that form the shell in which they reside, 
are more or less connected with it by muscular or membra- 
naceous attachment, or by the permanent spiral form of the 
posterior part of the body; and that the body of the animal 
complies with the inequalities of the chamber of the shell, or 
rather that the shell is moulded upon the body, so as to be 
in contact with it in every part. So careful are they to fill 
the cavity to its very summit, that when from their increase 
of growth the apex of the shell is vacated in consequence of 
its straightness, either that part is removed by the animal, and 
additional calcareous matter is secreted to close the aperture 
thus formed, or it is permitted to remain, and the cavity is 
filled up by the same secretion; of the former process we 
have an instance in Bulimus decollata ; and of the latter many 
instances occur, familiar to the knowledge of conchologists. 
The Ocythoe offers to our consideration a remote deviation 
from these ordinary laws which apply to the testaceous 
mollusca, inasmuch as it only resides in the last volution or 
body of the shell. In the specimen above described, the 
sides of the abdomen are slightly canaliculated, in conformity 
with the sculpture of the inner lateral surface of the shell ; 
but it is worthy of remark, that the portion which corresponds 
with the most unequal part of the chamber, the carina, is not 
at all indented ; which fact induces the supposition that the 
shell does not fit the body, and of course was not made for 
it, otherwise it does not seem probable that the body would 
