57 
iruEute ; membranes of the anterior arms rounded or suborbicular, 
extending half way to the base of the arms ; periphery occupied 
by the attenuated portion of the arm, which near its extremity 
passes upon the disk of the membrane, and terminates abruptly 
near the base of the expansion ; the membrane is carinately de- 
current on the inferior surface of the arm near the base of which 
it terminates ; the inferior surface of the membrane is brassy, and 
more numerously maculated than the superior, which is pale. 
Length from the disk to the tip of the abdomen 2 inches. 
Length of the abdomen 
Greatest breadth of abdomen 1 ‘lio 
Length of the alated arms 2| 
Length of those of the opposite side 5 
Eggs subovate, attached to a delicate pedicle by a small basilar 
tubercle. These fill the involuted spire in the specimen, besides a 
considerable portion of the body of the shell. t 
The suckers are very like those of 0. Cranchii, but the arms 
are much more elongated, and the abdomen longitudinal with 
respect to the head. This animal seems not to be unfrequently 
the prey of some of the larger fishes, for in addition to the in- 
stance above mentioned, Bose informs us that in his passage between 
Europe and America, he found a specimen in the stomach of a 
CorpJisena equiselis, Gmel., but very much decomposed ) and in 
the museum of Mr. Peale, in this city, a fine Argonauta occurs, 
which was taked from the stomach of a shark. 
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 molluscous animals 
that form the shell in which they reside, are more or less connected 
with it by muscular or membranaceous attachment, or by the per- 
manent 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 ad- 
ditional calcareous matter is secreted to close the aperture thus 
formed, or it is permitted to remain and the cavity is filled up by 
7 
