68 



the same secretion ; of the former process we have an instance in 

 Bulimus drcollata ; and of the latter, many instances occur, familiar 

 to the knowledge of conchologists. The Ocytlioe offers to onr 

 consideration a remote deviation from these ordinary laws which 

 apply to the testaceous mollusca, inasmuch as it only resides in the 

 last volution or hody of the shell. In the specimen ahove de- 

 scribed, the sides of the abdomen are slightly canaliculated, 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 

 fit 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 ; 

 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 Ocytlioe, 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 Ocytlio'i ascends to 

 the surface of the water by exhausting its shell of the included 

 water ; for if this were the fact, those females, whose shell is in 

 great part filled with eggs, could not visit the surfiice. But 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 stnicturc and appearance approach nearest 

 to Argmimita are unquestionably to be found in the Pteropoda ; 

 and the examination of Carinaria, Atlanta, and Spimtdla, woxdd 

 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 



