12 



triedral processes (o. pi. 1 ; m. pi. 2; b. fig. 2. pi. 3.) ; the inferior part (n. pi. 2.) 

 is thin, smooth, and concave, and rests upon the funnel. 



The hood or flattened part, which I have considered as surmounting the head, 

 (the position of the animal being determined by the nervous system,) is of a 

 white colour internally, and of a fibrous texture, resembling dense corimn, but is 

 doubtless muscular, and in creeping (the position of the animal being reversed,) 

 seems calculated to act as its chief locomotive organ. In the supine position of 

 the animal it bears considerable analogy to the foot of a Gasteropod ; and in a 

 state of rest and retraction it would serve as a rigid defence at the outlet of the 

 shell. The dimensions of this part are in length three inches and nine lines, in 

 breadth at the base three inches, at the apex seven lines. The apex (c. fig. 1 . pi. 3.) 

 of the triangular hood is anterior ; it is truncate, and terminates in a thin edge, 

 which is rounded at the angles and shghtly notched in the middle. The hood in- 

 creases in thickness towards the base, which is deeply excavated (d. fig. ]. pi. 3; 

 c. pi. 4.) ; and the angles form two rounded flattened processes (e. fig. 1. pi. 3; 

 b. pi. 4.), whose margins are thin, and project free to the extent of four lines. 



The exterior of the hood presents three superficies, whereof the middle and 

 superior one (/. fig. 1 . pi. 3 ; a. a. pi. 4.) is plane, and bounded by nearly parallel 

 lines, the space included being nine lines in breadth ; while the lateral superficies 

 (n. pi. 1 ; g. fig. 1. pi. 3.) are sinuous, and incline towards the sides of the head, 

 but are separated from the digitations by a narrow groove {q. pi. 1 ; h. fig. 1 . pi. 3.). 

 The papillae are chiefly observable on these surfaces, while on the middle surface 

 they are only to be seen towards the anterior part. To the large concavity at 

 the base of the hood are adapted the involuted convexity of the shell and the 

 fold of the mantle before mentioned ; but lest the shell should encroach too 

 much upon the hood and impede the freedom of its motions, or be itself, in the 

 act of creeping, dragged along the ground, it is supported by a semilunar ridge 

 (i. fig. ]. pi. 3.), which rises from this concavity about an inch from the pos- 

 terior margin of the hood. It is from this ridge that the mantle is immediately 

 continued to form the concave fold {a. b. fig. 1. pi. 3.)*. 



* It is worthy of remark, that in Sepia and Loligo there exists a corresponding ridge at the back 

 part of the head, beneath the anterior extremity of the rudimentary shell possessed by these genera ; 

 while in Octopus, Ocythoe, and some of the species of Eledone, no such jjart exists, and the mantle is 

 continued smoothly and uninterruptedly from the head to the back of the animal. 



