60 U.S. NATIONAL MUSEUM BULLETIN 291 



Between species, however, there are greater, consistent differences in 

 sucker dentition ; hacidifera has a greater number of teeth on the arm 

 suckers than does ahyssicola. Suckers of ahyssicola of 28 mm ML have 

 about eight protuberances around the aperture. Of these, the four 

 distal ones are long, truncate, widely set teeth, and the four proximal 

 ones are small, blunt, widely set knobs. On specimens of 38 mm ML 

 the number of teeth increases to 9-14 (usually 12) with the distal 4-7 

 teeth long, truncate to rounded, and widely spaced and the proximal 

 teeth knoblike. Smaller suckers from the same specimen have fewer 

 teeth. In specimens 56 mm ML the arm suckers bear from 8-18 teeth 

 depending on the diameter of the ring. The larger rings generally 

 average 10-14 widely spaced protuberances with long, truncate to 

 rounded distal teeth and short, blunt proximal knobs. Occasionally 

 a medium-sized ring will have more very closely packed teeth than 

 normal (up to 18). 



B. hacidifera of comparable size to B. ahysi^icola has slightly 

 smaller sucker apertures but a greater number of protuberances. The 

 larger sucker rings of the holotype (37 mm ML) have 18-26 (average 

 22) teeth. The teeth on the distal half are short, truncate to rounded, 

 and closely packed, and they grade proximally into small, very closely 

 packed knobs. The teeth on some rings are so closely packed that theii 

 lateral edges are in contact. Medium-sized teeth have about 16 pro- 

 tuberances. Exceptionally closely packed teeth and teeth on medium- 

 sized rings tend to be rounded and knobby, not truncate. Earely, 

 teeth will be about twice as wide as normal or about two times longer 

 than broad. 



During ontogeny teeth are added rapidly to the rings of hacidifera^ 

 but during comparable growth in ahyssicola. the number of teeth be- 

 comes stabilized (pis. 10 f-h; 9 b-d, f, g; 4 c-g; 5 o-i). This should 

 serve warning about placing too much emphasis on sucker dentition 

 without considering the age (size) of the specimens. 



The dentition of suckers from the tentacular clubs and the buccal 

 lappets does not seem to differ so noticeably between the two species. 

 Again, dentition varies but both species have about the same number 

 of points on the sucker rings; both club suckers and buccal suckers 

 have 8-12 teeth and knobs. 



Table II summarizes the diameters of arm, club, and buccal lap- 

 pet suckers for the two species of Bathyteutkis. The suckers of ahyssi- 

 cola tend to be slightly larger than those of hacidifera. 



