328 i- IJIMA AND S. IKEDA. 



this side little or no soft connective-tissue, so richly de^'eI()])ed within 

 the Avebs as well as over the outer surface of the arms. The entire 

 skin is on the whole smooth, at any rate by no means so flabby as on 

 tlie outer side of the umbrella. This difference in the amount of skin 

 on the two surfaces is assuredly a provision, by which the animal is 

 readily enabled by special exertions of its muscles, to ;issume a shape 

 concave on the lower side, as, for instance, when it would attach itself 

 by means of suckers to a projecting substratum or when it would 

 exercise swimming motion by alternate closure and expansion of its 

 arms. We believe the kind of locomotion just mentioned is of much 

 greater moment to (Jpistliotciiiliis than to most other Cephalo})ods, since 

 the ejection of water from the ccjmparatively small branchial chamber 

 and siphon can not but be of subordinate signihcunce. 



The mouth is situated somewhat eccentrically, i.e., a short distance 

 nearer to tlie free edge of the dorsal web than to that of the ventral. 

 Its position about corresp<mds, on the superior aspect of the animal, 

 to the middle of a line connectirjg the anterior ends of the lins. There 

 is a finely verruca ted buccal membrane jiresent in the mouth. The 

 laws show no characteristic features that seem to be woi'tli noticiu"- 

 (figs. 4 & 5). We have sought in vain for the radula, but will not 

 positiNcly assert its total absence. 



The arms are subequal. The longest is the second lateral arm, 

 after which the ventral, the first lateral and the dorsal arms are suc- 

 cessively shorter in the order mentioned. As seen after denuding 

 them of skin, they are rather stout and are thickest at the base, Avliere 

 they come in contact with one another and whence they gradually 

 taper off towards the tips. According to Verrill, the arms of 

 (>. A(jassizn are mucli narrowed towards the bases and these are said 

 to be not in contact, — a descrij)ti«m presumaljly based solely on their 

 external appearance on the inferior side, where the suckers decrease in 



