426 



PROCEEDINGS OF THE ACADEMY OF [July, 



the arm; along the ventral margin of the sucker-bearing area is a 

 delicate hyaline swimming membrane supported by a series of 

 fleshy lappets about equal in longitude to the hooks opposite which 

 they lie. Second arm also with 12 hooks (though on the right second 

 arm of another specimen 14 hooks were counted) and otherwise in 

 all essentials like the first. The third arm likewise has 12 hooks 

 succeeded by minute suckers at the tip; it is, however, more robust 

 than any of the others; a very broad conspicuous hyaline mem- 

 branous keel, unadorned with chromatophores on either surface, 

 runs along the outer margin, at its widest point (near the middle) 

 exceeding the diameter of the arm itself; ventral margin furnished 

 with a hyaline swimming membrane as above, but its trabecule are 

 much longer and larger. Ventral arm (PL IX, fig. 4) with 11-12 hooks 

 and no suckers, the whole extremity of the arm being bare except for 

 the curious terminal organs described below; longer and more gradually 

 tapering than the other arms, the hooks slightly smaller; devoid of 

 swimming membranes, but there is a well-developed keel along the 

 outer (dorsal) angle; the tip of each ventral arm is occupied by a 

 longitudinal series of three large, ovoid, heavily pigmented, bead-like 

 organs of a blackish color succeeded distally by one or two minute 

 rudiments of similar structures where the tip of the arm suddenly 

 tapers to a point; these are little protruding and have the super- 

 ficial appearance of being enveloped within the substance of the 

 arm itself, though really enclosed in the integument on the side of 

 the latter; in size the central organ perhaps slightly surpassing 

 the others (PL IX, fig. 1). 



As all the specimens seen are females, the hectocotylized arm 

 and other sexual characters have not been observed. 



Tentacles slender, about the length of the mantle, sides com- 

 pressed and somewhat flattened, inner surface of stalk flattened. 

 Clubs little or not at all expanded, the distal two-thirds armed with 

 four distinct crowded rows of minute suckers, some 74 to 76 in all, 12 

 regularly diminishing in size toward the tip; proximal to these and 

 projecting well out beyond the ventral margin are two very large, 

 elongate, slender, strongly incurved, sharply pointed hooks pro- 

 jecting for some distance from their large fleshy bases; opposite 

 these along the dorsal margin a single series of exceedingly minute 

 -hort-pediceled suckers, usually four in number and apparently 



12 Cf. the figure given by Chun of A. morisii 9 (1910, pi. 8, fig. 3), where but 

 about 40 such suckers are shown occupying a relatively much smaller proportion 

 of the entire club. 



