ANNOTATED LIST. 25 
TROPIOMETRID£E. 
Tropiometra afra. 
Antedon afra Hartlaub. 1890. Nova Acta Akad. Germ., 58, p. 86; pl. 5, figs. 50, 52. 
Tropiometra afra A. H. Clark. 1907. Smithson. Mise. Coll., 50, p. 349.—1918. Siboga Comat., pl. xxviii, fig. 106. 
In his “‘Recent Crinoids of Australia” (1911, p. 780) Mr. A. H. Clark says that only 
three Australian specimens of this fine species were at that time known, and two of these 
were from Bowen, Queensland. In his Siboga Comatulids (1918) he gives the range of the 
species as: Australia, except southern coast, to northwestern New Guinea. We were so 
fortunate as to obtain three specimens of afra at Mer, all found among the stag-horn corals 
of the extreme margin of the southwestern reef, a region accessible only at the lowest tides. 
They attracted attention by their very dark color, their extreme rigidity, and their inert- 
ness. The color, at first sight black, proved on closer examination in bright light to be 
deep purple. Unlike the other comatulids watched under their natural conditions, afra 
was erect and apparently rigid, firmly attached by its numerous, long, stout cirri to a branch 
of coral. There was no graceful movement of the arms, nor did they sway freely back 
and forth in the currents of water as did those of the large dark-colored Comanthus near by. 
In pail or basin at the laboratory, afra remained most inert, making no efforts to move and 
showing no response to mechanical stimuli. 
ANTEDONID£E. 
Dorometra nana. 
Antedon nana Hartlaub. 1891. Nova Acta Akad. Germ., 58, p. 89; pl. 5, figs. 57, 58. 
iidenee nana A. H. Clark. 1909. Vid. Med., p. 192.—H. L. Clark, 1915. Carnegie Inst. Wash. Pub. No. 212, 
Dicenere nana A. H. Clark. 1917. Jour. Wash. Acad. Sci., 7, p. 128. 
This is a widespread little comatulid, ranging from the Maldive Islands to Tonga, 
north to Macclesfield Bank and south to Torres Strait. The two specimens which we found 
at Mer are very unlike in coloration but in other respects seem to be identical. The first 
was taken on the southwestern reef, October 10, 1913, and attracted attention because of 
its very dark color and delicate arms. On being detached from the piece of coral and placed 
in a bucket of sea-water, it began to swim, and its activity, so different from the inertness 
of most of the comatulids collected, was very interesting. ‘‘Swimming was accomplished 
by using the arms in sets of five alternately, so that when arms 1, 3,5, 7,and9 were brought 
up almost vertically over the disk, arms 2, 4, 6, 8, and 10 struck backward forcibly with 
pinnules fully extended, until they nearly met behind the cirri. Only a single stroke was 
made but as arms 2, 4, 6, 8, and 10 were relaxed and drawn in and upward over the disk 
another similar stroke was made by the alternating five arms. Of course the movement 
was much more rapid than a description indicates, but it decreased in rapidity as the co- 
matulid became fatigued. At the start the strokes were at the rate of about 100 per minute 
but they rapidly dropped to much less than that and usually ceased altogether in less 
than a minute. Each stroke appeared to carry the individual about the length of its own 
arms.” ! This specimen of nana had arms 40 to 45 mm. long and the color was black, with 
a purplish tinge in bright light, though the cirri were light brown. On October 27 a second 
individual was discovered, far out on the southwestern reef; while similar in its reactions, 
this was light brown in color and was not recognized as identical with the dark-colored 
one until after returning to Cambridge. 
1 Carnegie Inst. Wash. Pub. No. 212, p. 110." 
