58 
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 de- 
scribed, the sides of the abdomen are slightly canalicuiated, in con- 
formity 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 in- 
dented ; which fact induces the supposition that the shell does not 
ft the body, and of course was not made for it, otherwise it does 
not seem probable that the body would be remote from the shell 
in one part, and impressed with its asperities in another. 
Such also is the form of the inferior part of the abdomen, that 
it never could have revolved in the cavity of the involuted spire 3 
yet we have never been informed that the vacated spire has been 
either broken or solidified. Neither is there any attachment what- 
ever between any part of the body and the including shell, by an 
organ appropriated to that office. In consequence of this organ- 
ization the Ocythoe cannot adapt itself to the form of the cavity 
in which it rests, or secure itself there so completely as the well 
known parasitic Paguri are enabled to do, in consequence of the 
pliability of their vesicular abdomen, and by the agency of their 
terminal hooks or holders. Such observations seem to afford pre- 
sumptive evidence of the parasitic nature of these animals. 
It does not appear to me probable that the Ocythoe ascends to 
the surface of the water by exhausting its shell of the included 
water 3 for if this were the fact, those females, whose shell is in 
great part filled with eggs, could not visit the surface. Eut the 
change of specific gravity is doubtless effected in its own body, by 
which it is enabled to sustain itself on the surface at will, or to 
descend to the bottom promptly at the approach of danger. 
The shells which in structure and appearance approach nearest 
to Argonauta are unquestionably to be found in the Pteropoba ; 
and the examination of Garinaria, Atlanta, and Spiratella, would 
almost lead us to suppose that the artificer of Argonauta is in 
reality of that division ; but if this supposition be indicated by 
the conformation of the shell, it does not seem to be corroborated 
