A. E. Verrill — Nortli American Cephalopods. 271 



along the outer angle, which is acute, while the ventral angle is 

 rounded. 



The tentacular-arms (Plate XXVIII, figs, la, 2) are long; when 

 extended, in fresh specimens, they reach back beyond the base of the 

 caudal fin. They are rather stout, rounded-trapezoidal along the 

 peduncular portion ; along the upper-outer angle a thin fold runs 

 from the base to the tip, becoming a wide carina on the backside of 

 the club ; two less marked folds run along the inner angles, defining 

 a narrow inner face, along the whole length, but on this face there 

 are no suckers, except close to where it begins to expand into the 

 broader face of the club; along the sides of the club, the marginal 

 membranes become much wider, rising to a level with the suckers. 



In the male of our species, one of the ventral arms (Plate XXVIII, 

 figs. 3, 3a) is strongly hectocotylized, somewhat as in Loligo. But 

 in this species it is the right arm, about as often as the left, that is 

 modified. Toward the tip of the arm, for some distance, the pedicels 

 of the suckers, especially of the outer row, become shorter, and the 

 bases of the sucker-stalks become larger, broader, and transversely 

 compressed, while the cups of the suckers themselves decrease rapidly, 

 till they become very minute, and on a number of the most flattened 

 and largest stalks, they are entirely abortive, in the case of the 

 medium sized males, but, very close to the tip, they may again become 

 normal. The inner row of suckers is more or less modified, in a 

 similar manner; but fewer of the sucker stalks are affected, and these 

 are, usually, not so extensively altered, though in the larger males 

 many of them are commonly destitute of cups and have the same flat- 

 tened form as those of the outer row, with which they are usually 

 united along the median line of the arm, forming a zigzag ridge. 

 In a very large male (J), with the right ventral arm modified, the 

 alteration of the sucker-stalks becomes obvious at about the 45th 

 sucker, and there are, beyond this, about 80 modified suckers, ex- 

 tending to the very tip ; of these about 30, in the outer row, are 

 represented only by the flat, lamelliform bases of the sucker-stalks, 

 without cups ; on the inner row, the small cups extend for about ten 

 suckers farther than on the outer. The lamelliform processes are united 

 medially in a zigzag line, along the entire tip. The modified part is 

 about an inch in length. This arm is as long as its mate, (though in 

 other specimens it is often shorter) ; but it is broader, stouter, and 

 more blunt at tip, both the inner face and lateral membrane being in- 

 creased in width. The younger males, 4 to 6 in, long, have the corre- 

 sponding suckers less extensively modified, and the cups, though very 

 much reduced in size, are usually present on all or nearly all the stalks. 



