310 A. E. Verrill — North American Cephalopods. 



forward as the posterior border of the eye, or even beyond it. Dorsal 

 connective cartilage long, tapering backwards, with a ver}- prom- 

 inent, broad, dorsal keel ; the anterior end is free and shaped like 

 the end of the pen. Siphon large, rounded anteriorly, with a broad, 

 bilabiate opening; lateral cartilages (PI. XL, fig. 1,/*) long and 

 narrow, subacute anteriorly, posterior end with a thin, rounded, 

 outer lobe ; median groove narrow. The connective cartilages of the 

 mantle (fig. 1,./") are simple, longitudinal ridges, fading out grad- 

 ually posteriorly. Head moderately large, usually narrower than 

 the mantle ; smaller in the male than in the female ; eyes large ; 

 nuchal crests (fig. 1, o/>) above the ear, formed by longer uppei', and 

 shorter inferior, oblique, longitudinal membranes, the two united by 

 a doubly curved, or V-shaped membrane, having its angle directed 

 forward, the whole having a rude, W-shaped form. 



Arms large, stout, the three upper pairs successively longer ; the 

 ventral ones a little shorter than the third pair, and a little longer 

 than the second pair. All the arms have narrow, thin, marginal 

 membranes, strengthened by strong, transverse, muscular ridges. 

 The first and second pairs of arms are trapezoidal at base ; third pair 

 stouter, compressed, with a keel on the middle of the outer side. 

 Suckers in two regular rows on all the arms, deep, very oblique ; 

 largest on the lateral arms ; those on the ventral arms are smaller, 

 but otherwise similar. Horny rings yellowish, or brownish (white 

 when fresh), strong ; on the larger proximal suckers the outer or 

 higher side is divided into about six broad, flattened, incurved teeth, 

 which are blunt, subtruncate, and sometimes even emarginate at tip, 

 remainder of margin nearly even ; the smaller suckers, toward the 

 tips of the arms, have the teeth longer, much more slender, and more 

 acute. 



The tentacular arm (PI. XXIX, fig. 2) with fresh specimens, in full 

 extension, may reach back nearly to the end of the body ; with pre- 

 served specimens it seldom extends beyond the middle of the caudal 

 fin • it is rather slender, compressed, and has a narrow, thin, mem- 

 branous keel along the outer edge, which becomes wider at the club ; 

 on the distal half of the club it is much wider and runs a little 

 obliquely along the back part of the upper side, where it is usually 

 folded down against the side, its inner surface being whitish. The 

 club is rather broad and thick, with a wide, scalloped, marginal 

 membrane along each edge ; these membranes are strengthened by 

 transverse muscular ridges, which commence between the large cen- 

 tral suckers and fork at the pedicels of the marginal ones. Along 



