546 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



united laterally. The IBr 2 (axillaries) are short, less than twice as long as the 

 IBri, broadly pentagonal or almost triangular. The IIIBr series are developed 

 entirely, or mainly, externally. IVBr series are occasionally present. The more 

 distal axillaries are relatively longer than the more proximal. The ossicles imme- 

 diately following each axillary are rhomboidal and are closely united interiorly. 

 The postradial series are either hi close lateral contact with flattened sides, or 

 free, or even well separated, laterally. Their outer borders are not thickened. The 

 division series and arm bases are strongly convex dorsally, and slight to moderate 

 synarthrial and articular tubercles are developed, giving the proximal portion of the 

 animal a characteristic rugged or rugose appearance. 



The arms are 14-40 (averaging about 30) in number and 65 to 150 (averaging 

 about 110) mm. long. They are usually long and slender, with a smooth dorsal surface, 

 and composed of about 200 rather short brachials. The first brachials are rhombic, or 

 almost rhombic, and are almost, or quite, completely united interiorly. The second 

 brachials are bluntly wedge-shaped, markedly longer exteriorly than interiorly, and of 

 almost the same size as the first, though slightly longer or shorter. The first syzygial 

 pair (composed of brachials 3 + 4) is oblong, broader than long, or sometimes about as 

 long as broad. The next five or six brachials are short and oblong, after which the 

 brachials become very obliquely wedge-shaped, or even triangular, and somewhat 

 longer, though still relatively short, later becoming bluntly wedge-shaped, after the 

 fortieth-fiftieth brachial shorter and more nearly oblong, and squarish toward the arm 

 tips. The first 3-5 brachials on the two outermost arms of each postradial series have 

 their outer sides flattened. 



Syzygies occur between brachials 3 + 4, again from between brachials 9+10 to 

 between brachials 23 + 24 (usually from between brachials 15 + 16 to between brachials 

 22 + 23), and distally at intervals of 5-17 (usually 7-14) muscular articulations. 



The pinnules of the first pair (P[ and P a ) are very delicate and slender and are 

 markedly smaller and weaker than the pinnules following. P t is 4.5 to 11 (usually 

 8-9) mm. long and may be composed of as many as 28 segments. It is moderately 

 thick at the base but becomes very slender and delicate in the distal half. P a is more 

 or less, and often markedly, smaller than Pp In a specimen from the China Sea in 

 which P! is 11 mm. long P a is 6 mm. long, with 21 segments. 



The pinnules of the second pair (P 2 and P b ) are markedly longer than, sometimes 

 twice as long as, those of the first pair (P t and P a ) but are always shorter (though some- 

 times not much shorter) than those of the third pair (P 3 and P c ), wliich are the longest 

 and stoutest pinnules on the arm. P 2 is 7.5 to 12 mm. long, with 18-27 (usually about 

 25) segments. It resembles P 3 but tapers more rapidly and abruptly in the proximal 

 portion and is slender from the fifth segment onward. P 3 is usually markedly longer 

 than P 2 , and it is also longer than P 4 . In its distal portion it becomes very slender 

 and flagellate. It is 9 to 18 mm. long, with 21-38 (usually 25-30) stout cylindrical 

 segments, of which some may be a little longer than broad. 



The pinnules of the fourth pair (P 4 and P d ) are almost always shorter than those 

 of the third pair (P 3 and P c ), though they are of variable length and may even be 

 somewhat longer. P 4 is 6 to 12.5 mm. long, with 16-27 segments, much smaller than 

 P 3 , intermediate in size between P 2 and P 3 , or as large as, or even slightly larger than, 

 P 3 . In one specimen on arms arising from a IIIBr axillary P 4 is 12.5 mm. long, with 27 



