2 12 
P., is 7o mm. long with i6 segments, resembling Pj but proportionately stouter; the 
distal edo-es of the third and following segments are slightly produced and finely spinous; as 
in P the dorsal edge of the second and third segments is slightly thickened. 
P, is 12 mm. to 13 mm. long with 22 segments, resembling P., but proportionately stouter. 
P is 5.0 mm. to 5.5 mm. long with 14 segments, similar in size to P^ but with the 
distal segments very slightly shorter. 
P. is 6 mm. long with 15 segments, slightly stouter than \\ and not tapering so rapidly. 
The distal pinnules are 6.5 mm. long with 16 segments, very slender, the segments 
beyond the two basal much elongated. 
The colour in spirits is deep purple, banded with yellowish at the articulations; the 
lower pinnules are yellowish. 
The specimens from Stats. 79" and 99, and the smaller from Stat. 96, have an arm 
length of between 25 mm. and 30 mm.; that from Maumeri is large, but badly broken. 
Iridometra A. H. Clark. 
Key to the Species of the Genus Iridometra. 
a^ Cirri not slender, the longest segments rarely more than four times as long as 
the median diameter, with the articulations only very slightly enlarged; P^ and 
P., with 16 — 19 segments; P„ slightly longer than Pj ■ 
b^ Pj, P, and Pg of appro.ximately the same length (P3 slightly longer than Pj,, 
which is slightly longer than P,), with 18 — 20 segments; cirri XL, 12 — 17 
(rarely more than 15), 10 mm. to 12 mm. long; arms 35 mm. to 60 mm. 
long (southern Japan; 23 — 192 [? 250] Metres) adrestine 
\y P^ and P^ of approximately the same length (P^ slightly longer than Pj), 
with 16 segments, but Pj shorter with 13 segments; cirri XXX — L, 15 — 19 
(usually 16 — 18), 10 mm. to 14 mm. long; arms about 50 mm. long (China 
Sea, near Hong Kong; 158 — 180 Metres) melpomene 
a- Cirri exceedingly slender with greatly elongated segments of which the proximal 
are at least six times as long as the median diaineter, with greatly swollen 
articulations; P^ and P„ similar, the latter usually slightly shorter than the former, 
with 1 1 — 13 segments; P^ smaller, with 8 — 9 segments, arms 40 mm. — 50 mm. 
long (Philippine Islands; 62 — 140 Metres) exqidsita 
1. Iridometra adrestme (A. H. Clark). 
A. H. Clark. Smithsonian Miscellaneous Collections (Quarterly Issue), vol. 50, 1907, part 3, 
p. 340 Antedon adrestine); p. 341 (Antedon ininitta). 
2. Iridometra melpomene A. H. Clark. 
A. H. Clark. Proc. U.S. National Museum, vol. 39, 191 1, p. 559 [Iridometra melpoincite). 
This species is infested with a curious amphipod parasite which bores into the disk, 
