178 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



again as long as broad. The next segment is slightly shorter, and the following are 

 about as long as broad. Those succeeding gradually decrease in length so that 

 the outermost 12-14 are subequal, about half again as broad as long. The tran- 

 sition and following segments have the distal dorsal edge raised into a coarsely 

 dentate transverse ridge which on the next 2 or 3 segments following the transi- 

 tion segment becomes concave and then rather strongly V-shaped, with a rather 

 large tooth at the apex of the V, and 2 smaller ones on either side. Distally the 

 median tooth gradually increases in prominence and the lateral teeth become less 

 marked untU on the 2 or 3 segments before the penultimate the lateral teeth nearly 

 or quite disappear, leaving the median tooth as a prominent median dorsal spine 

 which is slightly curved distalward. 



The opposing spine is median, slender, slightly curved distalward, equal in 

 height to about one-third the width of the penultimate segment; it is about as long 

 as the 1 or 2 spines preceding. The terminal claw is about half again as long as 

 the penultimate segment, stout and strongly curved basally but becoming straighter 

 and more slender distally. 



The ends of the basal rays are visible as rather prominent tubercles in the angles 

 of the calj'x. 



The radials are concealed by the centrodorsal. The IBri are oblong, very short, 

 closely united laterally, and usually somewhat concealed by the centrodorsal. The 

 IBr2 (axillaries) are short, broad, almost or quite triangular, from two to two and 

 one-half times as broad as long, nearly or quite in contact laterally. The IIBr 

 series are 4 (3+4), rarely 2, well rounded dorsally; the pinnules borne by the IIBr2 

 are usually almost, sometimes quite, in apposition. The IIIBr series are 3 (2 + 3), 

 usually not developed on more than half the rays and often altogether absent. The 

 IVBr series are 3 (2 + 3), but are rarely developed; when present they are widely 

 separated from their neighbors. 



The arms are 12-35 in number, most commonly 18-24, from 100 to 125 mm. in 

 length. The first brachials are wedge-shaped, longer outwardly than inwardly, 

 about twice as broad as the median length, and entirely united interiorly. The first 

 syzygial pair (composed of brachials 2 + 3) is most commonly about twice as broad 

 as long, or somewhat broader. The next 2 or 3 brachials are oblong, about three 

 times as broad as long, and those following become more or less, in the best 

 developed individuals only slightly, wedge-shaped, three or four times as broad as 

 long, soon gradually becoming oblong again, in the outer three-fourths of the arm 

 being regularly oblong, approximately four times as broad as long, but becoming 

 longer again and more wedge-shaped at the tip. After the first 3 the brachials have 

 very prominent finely spinous distal ends. The elements of the IIBr and IIIBr 

 series also usually have their distal ends everted and prominent. The arms usually 

 increase more or less markedly in width from the first to about the twentieth 

 brachial, in extreme cases being twice as broad here as at the base; beyond the 

 twentieth brachial the arm remains of practically the same width for some time, 

 then tapers gradually to the tip. In many individuals, especially those with a com- 

 paratively small number of arms, this increase in width of the proximal portion of 

 the arm is but little marked. 



