A. M Verrill — North American Cephalopods. 261 



wider on the ventrals than on any of the others. Each sucker-pedi- 

 cel arises from a muscular cushion, that is slightly raised and rounded 

 on the inner side ; these, alternating on the two sides, leave a zigzag 

 depression along tlie middle of the arm ; from each of these cushions 

 two thickened muscular ridges run outward to the edge of the lateral 

 membranes, one on each side of the pedicels of the suckers. These 

 transverse muscular ridges give a scolloped outline to the margin of 

 the membranes. These marginal membranes are narrowest and the 

 suckers are smallest on the ventral arms. The dorsal and lateral 

 arms are strongly compressed laterally, but slightly swollen or con- 

 vex in the middle, and narrowed externally to a carina, which is 

 most prominent along the middle of the arms, and most conspicuous 

 on the third pair of arms. The dorsal arms are rather more slender 

 than the second pair, and were probably somewhat shorter. 



The left arm of the second pair has the tip preserved, with all its 

 suckers present. On this arm there are 330 suckers, in all. The total 

 length of the arm is 26*25 inches. The first 50 suckers extend to 

 12*25 inches from the base ; the next 50 occupy 4*5 inches ; the next 

 50 cover 3*5 ; the next 100 occupy 4*25 inches; the last 80 occupy 

 1*75 inches. This arm is "80 of an inch in transverse diameter, near the 

 base ; 1*20 inches from front to back ; breadth of its front or sucker- 

 bearing surface (without the lateral membranes), is, where widest, 

 near the base of the arm, "50 of an inch ; the width gradually 

 decreases, to *18 of an inch at 20 inches from the base ; beyond this 

 the arm tapers to a very slender tip, with numerous small crowded 

 suckers in two regular rows. At the base (Plate XXVI, fig. 4) 

 there is first one very small sucker ; this is succeeded by two or three 

 much larger ones, increasing a little in size ; beyond these are the 

 largest suckers, extending to about the 25th, beyond which they 

 gradually change their form and regularly diminish in size to the 

 tips. The larger proximal suckers, up to the 25th to 30th, are rela- 

 tively broader than those beyond, and have a wider and more open 

 aperture, and a more even and less oblique horny ring, which is 

 sharply denticulate around the entire circumference, with the denti- 

 cles rather smaller on the inner than on the outer margin, but similar 

 in form. These are about '31 of an inch in external diameter. They 

 show a gradual transition to those with more oblique rims and 

 smaller apertures. Beyond the 30th, the horny rims become de- 

 cidedly more oblique and one-sided, with the denticles nearly or quite 

 abortive on the inner side, and larger and more incurved on the outer 

 margin, while the aperture becomes more contracted and oblique. 



