ON THE ARGONAUT. 529 



side the whole length of the carina, leaving a space between 

 them, within which we perceived to open, the extremity of the 

 tube of the animal ; whilst the four others were disposed, two 

 to the right and two to the left, in the middle part of the 

 opening, contracted and irregularly bent back. As to the 

 higher arms, their disposition was altogether different from 

 that of the others. Prolonging themselves towards the re- 

 treating part of the spire, one on each side, they encountered 

 the keel by the tangent line, and, without again quitting it, 

 stretched out as far as its exterior extremity, insinuating them- 

 selves between the tubercles, and in such a manner that there 

 remained in the median line of the keel, only a narrow space 

 that was not covered. 



The membranous portions of these arms, dilated beyond 

 anything we could have pictured to ourselves while knowing 

 the animal merely by specimens preserved in spirits of wine, 

 were spread over the two lateral surfaces of the shell, in 

 such a manner as to cover it completely, from the base of the 

 hard edge [bord calleux] to the anterior extremity of the 

 edge of the opening, and consequently the keel. The appli- 

 cation of these membranes was direct, and without any puck- 

 ering or irregularity whatever : the lower part of the two large 

 arms, being completely stretched, formed a kind of bridge 

 over the cavity left between the back of the mollusc and the 

 retreating portion of the spire, in which the extremity of a 

 cluster of ova was floating. 



We have thought it right to bring forward this new descrip- 

 tion, in order to make more evident what is wanting in the 

 plate which accompanies M. de Blainville's letter, and in 

 which the artist has not sufficiently pourtrayed the peculiar- 

 ity which relates to the membranes of the large arms. It, in 

 fact, appears to us, that the animal being represented as con- 

 tracted in its shell, the six arms which are not membranifer- 

 ous ought not to float freely about on the outside, but that 

 they should be bent back within, as we have just said, and 

 as we represent them in our third plate ; 1 then the siphon 

 ought not to appear, not being of sufficient length to do so ; 

 and the large arms, instead of taking the direction along the 

 base of the lateral angle of the shell, ought to carry them- 

 selves directly lengthwise along the keel, to follow it to its 

 extremity, and the membrane should carpet the surface of 

 the shell. 



It is very true that when the mollusc contracts itself, it 

 frequently draws in, more or less completely, its large arms 



1 Plate 6 of our Supplementary Illustrations. — Ed. 

 Vol. III.— No. 35. n. s. 3 m 



