ANNOTATED LIST. 115 
Ophiothrix trilineata. 
Litken. 1869. Add. ad Hist. Oph., pt. 3, pp. 58 and 100. 
(Plate 16, Figures 4 to 6; Plate 33, Figures 4 and 5.) 
It is a remarkable fact that this brittle-star, one of the most abundant and character- 
istic inhabitants of the reef-flats at Mer, was not taken in Torres Strait by the Alert, the 
Challenger, or Dr. Semon, nor did we find it at Thursday Island or Badu. It does not seem 
to occur in the Aru Islands, as Merton failed to find it there. It has not been found on any 
part of the Australian coast, though Bell (1894) reports it from northwestern Australia 
in 20 to 85 fathoms. Yet it ranges right across the Indian Ocean from Mozambique, 
Zanzibar and Mauritius (where it is common) to and throughout the East Indies and east- 
ward at least as far as Samoa. 
At Mer it occurred generally among living corals, and particularly in the dead basal 
portions of colonies of Seriatopora. It literally swarmed in such situations, and when these 
colonies were broken apart the activities of these beautiful brittle-stars were most inter- 
esting. There is much individual diversity in color, spinulation, and proportions, yet 
the specific characters are remarkably constant, and rare indeed is a specimen the identifi- 
cation of which need give any trouble. As regards the spinulation of the disk, the diversity 
is only in the number and the length of the spinules; these may be very few or there may 
be quite a number, but they are never crowded and are usually widely separated; they 
are sometimes rather short and sometimes very long (14 to 14 disk diameter), but they are 
always slender, smooth, and acute; aside from them, there are no thorns, stumps, grains, 
granules, or spinules of any kind on the disk. 
In color there is wonderful variety, but in the presence of 3 light stripes and 2 (or 4) 
very dark stripes on the upper side of each arm there is extraordinary constancy; occasion- 
ally, on the basal part of the arm, the stripes become irregular and broken and transverse 
markings become prominent (plate 16, fig. 4), but examination with a lens of the distal 
part of the arm, especially if there be a regenerating tip, reveals the characteristic stripes. 
There is much diversity as to the relative width of the stripes. The usual typical appear- 
ance is well shown in figure 6, plate 16, but sometimes the light stripes are much narrower 
than the dark ones, or, on the other hand, the median light stripe is sometimes so expanded 
that it occupies most of the upper surface of the arm. Asa rule, the light stripes are white, 
cream-color, or pale yellow, but often, especially when the median stripe is greatly ex- 
panded, they become yellow or even orange. In one young specimen the whole upper sur- 
face of the basal part of each arm was bright orange. The ground-color of disk and arms 
is usually green of some rather deep shade, but it may be purple or blackish. The arm- 
spines are usually tinged with green or purple, but not rarely are bright red (pl. 16, figs. 
5 and 6). Red, orange, and yellow are very fugitive colors and rarely show at all in pre- 
served specimens. The latter are commonly deep blue, deep purple, or deep greenish, with 
sometimes markings of white or whitish on the disk, besides the whitish stripes on the 
arms. The ground-color may be light bluish, purplish, or grayish, especially in old dry 
specimens. The character of the disk, combined with the stripes on at least the distal part 
of the arm, makes the identification of even poor specimens easy. 
Ophiothrix virgata. 
Lyman. 1861. Proc. Boston Soc. Nat. Hist., 8, p. 82—IKoehler. 1904. Mém. Soc. Zool. France, 17, p. 80, 
figs. 36-40. 
The discovery at Mer of this rare brittle-star is of no little interest, for since the holo- 
type was described from the Gilbert Islands, the specimen collected at Amboina by Brock 
seems to be the only individual that has been found. Only three individuals were taken 
at Mer. One of these is young, with the disk not 5 mm. across, but the other two are 
