332 



I. IJIMA AND S. TKEDA. 



The presence of a dorsnl cartilage could only be ascertained after 

 pirtinlly rciuosinfj^ the dors:d skin. It is a single, transversely 

 situated, cartilaginous l):ir {c, fig. 6), no part of which is directly 

 continued into the fins. Here is another ini])ortant point of ditference 

 from 0. J<i((y!si~i'i, in which it should occur in two separate pieces, each 

 contained in the fin itself. The simple cartilaginous bar of the present 

 s])ecies, is thin, 1 mm. broad (:intero-posteriorly), mm. and 11 mm. 

 long respectively along the anterior «and the posterior edge. It is 

 situated al)out 4 mm. behind tlie level of fins, beneath the thick skin 

 nnd closely over the visceral sac above the posterior part of the liver 

 {(I.e., fig. 9). From its either end a muscle takes its origin (m., fig. 6). 

 The latter soon bends forwards and inserts itself at the fin-base of the 

 resj^ective side. 



Cutting open the nLantle-cnvity, the siphon, of which but a small 

 portion was visible from outside, is exjx^sed in its entire length (fig. 7). 

 It I hen measures 7 mm. in length and about as nmch in breadth at 

 the base, reja-esenting a nmcli fiattened cone in its general shape. Its 

 h^wer wall, which corresjionds to the dorsal aspect of the siphon of 

 normally «haped Cephalop(3ds, is completely adnate with the connective 

 tissue of the ventral web. Its muscular sul)stance splits, just beneath 

 the anus, into two bands, whicli after running antero-laterally beneath 

 the branchial chambers, finally become lost in the connective tissues. 

 The upper wall of the siphon is covered by the chromatophore-bearing 

 skin directly continuous witli that of the outer surfice of the umbrella 

 and is reflected outwards along it free edge at the siphon -basis, especi- 

 ally so at two lateral positions which evidently serve as the so-called 

 button (hut., figs. 7-9). 



The mantle-edge at the branchial aperture is reflected inwards 

 (ci). The reflected edge is laterally continued into a fold (/^), which 

 incom])let('1v shuts off the branchial chandlers on the median side and 



