Boone, Mollusca, Cruises of "Ara" and "Alva" 347 



meters in diameter, so that the pallial aperture extends dorsad 

 only a very brief distance beyond the eye-ball which it partially 

 encompasses posteriorly. Ventrally the mantle margin is sinuous, 

 being concave in variable degree beneath the funnel and convexly 

 advanced on either side of this. 



The head is 80 to 90 per centum as long as wide, quite flattish 

 dorsally and somewhat excavate ventrally beneath the siphon. 

 The eye is large, conspicuous, tumid. The funnel is elongate, coni- 

 cal, the apical portion cylindrical, nearly or quite extending to the 

 bases of the fourth pair of arms, with the apical aperture small, 

 the siphon wall thick, interior of the apex minutely striate longi- 

 tudinally, the small valve is spoon-shape, located on the dorsal 

 wall immediately posterior to this striate area and in turn is fol- 

 lowed posteriorly by an area of strong transverse striation. The 

 funnel organ is posterior in position. 



The arms are rather stocky, about as long or slightly longer 

 than the body and of unequal lengths, the arms decreasing in the 

 order 2, 3, 4, 1, the inequality between the dorsal and ventral pairs 

 being slight and the second pair normally exceeding the third pair 

 by a very short distance. There is a fugitive external carina of 

 skin present on pairs one, two and three, this attaining highest 

 development on the third pair of arms ; the fourth pair are exter- 

 nally rounded. The interbrachial web is very rudimentary be- 

 tween the arms of the dorsal pair as well as of the ventral pair, 

 being somewhat deeper between the arms of the first and second 

 pairs, while between the third arm and related fourth one the 

 web is characteristically developed, supporting the base of the 

 tentacular arm. The suckers on all four pairs of sessile arms are 

 close-set in dual series proximally for about the first two or three 

 pairs, beyond which these pairs are displaced alternately so that 

 four rows exist, closely crowded, with the suckers set on stout, 

 flexible, conical pedicels, the cups subspherical, with a distinct 

 indentation near their attachment to the pedicel. The chitinous 

 ring within the sucker is prominent, subcircular, frequently con- 

 vexly produced unequally in the larger suckers and having an 

 oval or elliptical lip-like small aperture. The ring appears devoid 

 of teeth but under high magnification is seen to be cut into an 

 irregular crenulation or rudimentary dentition on the deeper side 

 of the larger suckers of the ring, but smooth in the smaller Cups. 



The left dorsal arm of the male is hectocotylized. This arm is 



