36 U.S. NATIONAL MUSEUM BULLETIN 291 



length to the base of the chib, but the dub tapers gradually to a blunt 

 termination. The sucker-bearing portion of the club is covered with 

 numerous, minute, closely packed suckers. The suckers originate with 

 a single sucker proximally ; the next few suckers are slightly scattered 

 and set apart, but the suckers increase in number rapidly and become 

 very closely packed. Suckers are evenly distributed over the club so 

 that no clearly defined pattern of rows exists; however, eight to ten 

 longitudinal rows of suckers occur on the sucker-bearing surface for 

 nearly the entire length of the club. Suckers decrease in numbers 

 only at the very proximal and distal ends of the club. 



The sucker-bearing portion of the club terminates in a bluntly 

 rounded area of suckers. An extremely small, papilla-like tip protrudes 

 distal to the sucker-bearing area and is continuous with the aboral sur- 

 face of the club (pi. 4b). A few minute knobs are located on the prox- 

 imal portion of the terminal papilla; these knobs probably are 

 precursors to suckers. Possibly the terminal papilla represents the 

 growing portion of the tentacular club. 



No protective membranes exist along the borders of the club ; only a 

 slight, pigmented line outlines the sucker-bearing portion of the club, 

 especially in its proximal half. A thin, low keel originates on the dorsal 

 aboral surface of the tentacular stalk just proximal to the first (proxi- 

 malmost) sucker of the club. The keel extends distally and broadens 

 gradually in the distal third of the club ; it terminates near the tip of 

 the club just proximal to the end of the sucker-bearing area. No addi- 

 tional keels or membranes are present. 



The suckers on the club are small and nmnerous ; about 525 suckers, 

 the largest 0.14 mm in diameter at the aperture, occur on the club of 

 a specimen 56 mm in mantle length. The diameter of the sucker aper- 

 tures in adults varies between 0.08 and 0.14 mm, depending upon the 

 size of the specimen. Some variation in dentition occurs, but in general 

 about 8-12 teeth and knobs are set around the aperture. The teeth that 

 occur on the distal half of the border generally are truncate, longer 

 than broad, and widely separated, although occasionally the teeth will 

 be shorter, almost square, or rounded, or very occasionally, triangular. 

 The larger suckers of a club from a specimen 28 mm in mantle length 

 (Elt. 1201; pi. 4j) have about 8-12 points around the aperture; those 

 with 8 or 9 j^oints have 4 to 5 long, truncate, widely spaced teeth and 

 4 to 5 small, rounded bumps or knobs; those with 11 or 12 points have 

 6 teeth and 5 to 6 knobs. Sometimes two teeth will be closely set and 

 very narrow as though earlier in ontogeny they had been a single tooth 

 that split in two. Larger specimens have club suckers with a few more 

 enlarged teeth so that rings with 9-13 points may have 5-8 long, trun- 

 cate teeth and 4 to 5 knobs (pi. 4k), Some large teeth are notched on 



