REPORT ON THE ECHINOIDEA—MORTENSEN 4 
that these ophicephalous pedicellariae are quite different from those 
of Tromikosoma, having no neck, and with the stalk simple, not tube- 
shaped as in the latter genus. 
The larger specimens are conspicuously pentagonal. 
The contents of the intestinal canal of the larger specimens was 
found to be mainly bits of land plants. 
HYGROSOMA LUCULENTUM (A. Agassiz) 
Phormosoma luculentum A. AGaAssiz, Challenger Reports, Zoology, vol. 3, pt. 9, 
Echinoidea, p. 97, pl. 9; pl. 10; pl. 10a, figs. 3-7; pl. 39, fig. 8; pl. 40, figs. 
31-86; pl. 44, figs. 25-27, 1881. 
Hygrosoma luculentum MortENSEN, Ingolf Echinoidea, pt. 1, pp. 59, 64, pl. 12, 
fig. 20; pl. 13, figs. 14, 16, 1903. — D6prRLern, Wiss. Ergebn. Tiefsee-Exped., 
vol. 5, Lief. 2, p. 143, pl. 17, fig. 2; pl. 39, fig. 1, 1906. —-KoEHLER, Investi- 
gator Echinoidea, pt. 3, p. 36, pl. 24, fig. 1, 1927-——MorTrENSEN, Monograph of 
the Echinoidea, vol. 2, p. 215, pl. 21; pl. 22; pl. 78, figs. 22, 28, 1935. 
Echinosoma luculentum A. AcAssiz and H. L. CLark, Hawaiian and other Pacific 
Echini, Echinothuridae, p. 163, 1909. 
Localities.—Station 5447; east coast of Luzon; San Miecuel Point 
bearing S. 7° W., 3.5 miles distant (lat. 13°28’00’’ N., long. 123°46’ 
18’’ FE.) ; 567 meters; bottom temperature 7.39° C.; green mud; June 
4, 1909. One specimen. 
Station 5506; off northern Mindanao; Macabalan Point Light, 
Mindanao, bearing S. 41° E., 12.2 miles distant (lat. 8°40’00’’ N., 
long. 124°31’45’’ E.); 479 meters; bottom temperature 11.83° C.; 
green mud; August 5, 1909. One specimen. 
Station 5512; in the vicinity of northern Mindanao; Camp Overton 
Light bearing S. 76° E., 14 miles distant (lat. 8°16’02”’ N., long. 
123°58’26”’ E.) ; 813 meters; bottom temperature 11.56° C.; gray mud 
and fine sand; August 7, 1909. One specimen. 
Remarks.—The specimens from stations 5506 and 5512, both of 
which are small, should perhaps rather be referred to H. hoplacantha, 
neither having the typical large broad-valved pedicellariae so char- 
acteristic of /wculentum. But there is, in the former at least, one 
pedicellaria intermediate between the coarse and the slender form, 
and in the latter the spines near the apical system appear to have 
been skin clad, which is another character of luculentum. But on 
the whole Zuculentum is so closely related to hoplacantha that it may 
be doubted even whether they are really different species, and unless 
very typically developed and well-preserved specimens are at hand it 
will probably not be possible really to distinguish between them. 
When the typical coarse pedicellariae are present, as in the specimen 
from station 5447, there is, of course, no difficulty in distinguishing 
them. 
Like H. hoplacantha, this species was found to feed mainly on land 
plants washed out to sea and sunk to the bottom. 
