Zoology.-] NATURAL HISTORY OF VICTORIA. [Mollusca. 



There is a transparent web, about 3 lines high, between the base of the 4th and 3rd 

 pair of arms, but none between the bases of the 3rd and 2nd ; between the 2nd and 

 1st or palmated arms the transparent web is about 3 lines high. 



Measurements. Ins. lines. 



Length of body from base of head ... ... ... ... 3 



Greatest width, about ... ... ... ... ... 2 



Length of anterior arm ... ... ... ... ... 5 9 



„ next arm ... ... ... ... ... 6 3 



„ next arm ... ... ... ... ... 8 9 



„ sucker line of posterior or palmated arm ... ... 10 6 



„ posterior arm to distal part of curve ... ... 5 7 



Width of membranous keel on outside of posterior arm ... 3 



Depth of arms near base ... ... ... ... ... 3 



Diameter of eye ... ... ... ... ... ... 9 



Width of cervical ligament ... ... ... ... 7 



Shell : moderately compressed ; periphery narrow, bituberculate ; sides with 

 narrow, transverse, radiating, arched ridges, occasionally branching, and with shorter 

 intercalated ones as they radiate towards the periphery, rising into longitudinal, ovate 

 tubercles, like grains of rice. Antero-posterior diameter of moderate specimen, 5 in. 

 6 lines ; width of periphery from tip of one tuberculated keel to the other, 9 lines ; 

 greatest transverse width of aperture (near middle), 2 in. 3 lines ; near margin, 5 

 ridges in space of one inch ; 4 tubercles along each ridge in space of one inch. 



Reference. — (Shell) = Argonauta oryzata (Meusch.) Mus. Geversianum = A. 

 nodosa (Solander) Portland Catal. = A. tnberculata (Shaw) Nat. Mis. v. 23, t. 995 

 = A. tuberculosa (Schumacher) Lam. Anim. s. Vert. 2nd edit. (Animal) = 

 Octopus raricyathus (Blainv.) = Ocytho'e raricyathus (Gray) Cat. B.M. Ceph. 

 Anteped. Pt. 1, p. 32. 



The beautiful objects popularly miscalled Paper-Nautili should 

 not really be compared with true shells, like that of the Nautilus, 

 to which the inhabitant is fixed by organic attachments, without 

 tearing which or destroying the life of the Cuttle-fish it would be 

 impossible to separate them. The Argonaut, or Paper-Nautilus, is 

 always excessively thin, white, imperfectly calcified, so as to be 

 slightly flexible when fresh, and totally unconnected with the 

 Octopus inhabiting it ; so that the so-called shell may be dropped if 

 the Cuttle-fish be frightened, without injuring any of the soft parts 

 of the animal. This want of connection between the Argonaut 

 and its inhabitant was known even to Aristotle. The animal, which 

 was called Ocythoe by Rafinesque, inhabiting the Argonaut shell is 

 shaped to fit in the inrolled spire by a peculiarity of form in the 

 body not found in any other of the Acetabulifera, namely, the 

 profile of the back being concave, while the front is convex ; 

 this recurving of the posterior end according in shape with the 

 cavity of the so-called shell, which is retained in its place by the 

 pair of enlarged, racket-shaped posterior arms bent backwards and 

 closely embracing it. 



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