244 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The cirri are XX-XXV, about 20. According to Carpenter a few of the segments 

 are longer than broad and the later ones are somewhat compressed laterally and more 

 or less distinctly carinato dorsally. In the figure the segments beyond the basal are 

 about as long as broad except for the last two which arc somewhat longer. 



The radials are partially visible above the interradial angles of the centrodorsal. 

 The IBr : are short, sharply convex, and very closely united laterally. The IBr 2 (axil- 

 lanes) are short, broadly pentagonal, and very convex in the center; a synarthrial 

 tubercle is present. The IIBr series are 4(3+4). The elements of the IIBr series and 

 in a lesser degree also those of the IBr series and the fourth brachial are in close lateral 

 contact and very distinctly wall-sided with sharp edges and the margin of the dorsal 

 surface a little depressed. The third and occasionally also the fourth brachial may 

 likewise be slightly flattened on both the outer and inner sides. One specimen has one 

 IIIBr 2(1 + 2) and one IILBr 3(2+3) series. 



The 1 1-20 arms are about 100 mm. long and are composed of about 120 brachials of 

 which the lowest are nearly oblong, those following triangular and as long as broad, the 

 succeeding becoming more wedge-shaped. The lower parts of the arms and the division 

 series often have somewhat prominent edges. 



On arms arising from a IBr axillary the first syzygy is between brachials 3+4 and 

 the next is from between brachials 5 + 6 to between brachials 14 + 15. On arms arising 

 from a IIBr axillary the first syzygy is usually between brachials 1 + 2 and the second 

 is from between brachials 8+9 to between brachials 11 + 12. The distal intersyzygial 

 interval is from 3 to 16, usually from 5 to 8, muscular articulations. 



P D is small, 7 mm. long with 20-25 short segments the lowest of which, and espe- 

 cially, the first, are broad, trihedral, and flattened against the arm, the remainder being 

 slightly carinate. Pi is a trifle longer with relatively long terminal segments and less 

 broad and more carinate basal segments. P 2 and the following pinnules are still longer 

 and stouter, 12 mm. in length, with the outer edges of the third and two to four following 

 segments much produced toward the ventral side so as to give them a broad and flat- 

 tened appearance. After P 3 the length of the pinnules decreases somewhat, but the 

 expansion of their lower segments is traceable until P ls or P 20 , after which they become 

 more slender with only the two basal segments broader than long. 



The disk is 10 nun. in diameter, much incised and completely plated both along the 

 ambulacra and at the sides. A pavement of anambulacral plates covers the gonads. 

 The pinnule ambulacra have well defined side plates alternating with and partly con- 

 cealing the sacculi, which are mostly small. 



The color in alcohol is light whitish brown. 



Notes. — After examining the Challenger specimens in the British Museum Gislen 

 wrote that in this species there are often syzygies between brachials 1+2 and 3+4, in 

 other words that the first four brachials are often united in two syzygial pairs. He gives 

 a diagram of the conditions in a postradial series with two IIBr 4(3+4) series. One 

 of these gives rise to two arms on one of which the syzygies are between brachials 1+2 

 and 10+11, while on the other they are between brachials 1+2 and 11 + 12. On the 

 other IIBr series the inner branch is undivided with syzygies between brachials 1+2, 

 4 + 5, 11 + 12, and 17+18. The outer branch is a IIIBr 3(2+3) series with the inner 

 arm having syzygies between brachials 1 + 2, 4+5, 11 + 12, 17+18, while the outer 

 arm has them between brachials 1+2, 8+9, 14+15, and 20+21. 



