426 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



first. The first syzygial pair (composed of brachials 3+4) is about as long as broad, 

 or slightly broader than long. The next four or five brachials are oblong, and those 

 succeeding are wedge-shaped or even triangular, broader than long, with very slightly 

 produced and overlapping distal ends, gradually becoming quadrate and more dis- 

 coidal again in the middle of the arm. 



Syzygies occur between brachials 3+4, again from between brachials 8+9 to 

 between brachials 22+23 (usually from between bracbials 13 + 14 to between brachials 

 16+17, and on arms arising from a IBr axillary with an extra one between brachials 

 8+9 or 9+10), and distally at intervals of 4-11 (usually 6-8) muscular articulations. 



PI is weak, slender, and flagellate. It varies in length from half as long as P 2 to 

 quite as long as the latter but is usually two-thirds to three-fourths the length of P 2 . 

 It measures 4 to 14 mm. in length but is usually between 9 and 1 1 mm. long. It is 

 composed of 14-27 (usually 17-22) segments, of which the first is twice as broad as 

 long, the third is about as long as broad, and those following gradually increase in 

 length so that the distal are three times as long as broad or even longer. 



P 2 is stouter, usually much stouter, than PI, usually markedly longer and never 

 shorter, composed of fewer segments, very stiff and styliform with a sharp spinelike 

 tip, straight and erect, recurved at the base, or recurved for its entire length. It 

 varies from 8 to 17 mm. in length and is usually between 10 and 15 mm. long. It is 

 composed of 9-18 (usually 10-15) segments of which the first is twice as broad as long, 

 the third is about as long as broad or somewhat longer than broad, and most of the 

 remainder, except the terminal, are three times as long as broad or even longer. The 

 terminal 4-6 segments are sometimes abruptly less in diameter than those preceding, 

 so that the pinnule appears to have a regenerated tip. Although three instances of 

 this have been reported from widely separated regions (the Philippines, Singapore, 

 and Ceylon), it may be the result of injury or of a diseased condition. 



P 3 resembles P 2 in character, but it is always shorter. It is commonly about 

 two-thirds as long as P 2 , but may be longer and even very nearly as long as the latter. 

 Its length varies from 5 to 14 mm., being usually between 8 and 12 mm. Its stoutness 

 in relation to P 2 is proportionate to the length of the two pinnules. P 3 usually is 

 composed of one to four fewer segments than P 2 , but occasionally it has the same num- 

 ber of segments, and rarely it has from one to three more. The segments number 

 from 8 to 14 and are most commonly 10-12. They are of the same proportions as the 

 segments of P 2 . 



P 4 is variable. It is typically and usually small, slender,, and flexible like the 

 following pinnules and thus very different from the enlarged and styliform P 2 and P 3 . 

 But it may be slightly longer than the succeeding pinnules and somewhat stiffened, 

 and in extreme cases it may, though much smaller than P 3 , be nearly three-fourths of 

 its length and more or less like it distally, differing more from the slender, weak, and 

 flexible P 6 than it does from P 3 . It varies from 3 to 9 mm. in length and is composed 

 of 8-12 (usually 9-11) segments. 



Notes. The specimen from the Macclesfield Bank is smaller than the type of 

 Carpenter's Antedon tuberculata from Challenger station 174 but is otherwise exactly 

 like it. 



The specimen from Annam, according to Gislen, has the cirri 11-14 mm. long, 

 with 19-21 segments. There are no dorsal spines, but an opposing spine is present. 



