REPORT GIST THE HOLOTHIJRIOIDEA. 
161 
Stichopus japonicus, var. typicus, nov. (PL VIII. fig. 2). 
Habitat. — Japan. May 1875 ; two specimens. 
The two specimens brought home by the Challenger Expedition have each a length of 
220 mm., thus being much larger than the previously known forms described by Selenka 
and von Marenzeller. In consequence of the existence of some differences I prefer for 
the present to consider the Challenger specimens as a variety, though it is most probable 
that they represent the older and more fully developed forms of Stichop>us japonicus, a 
supposition confirmed not only from the greater size, but also from the presence of well- 
developed genital bundles on each side of the dorsal mesentery; neither Selenka nor 
von Marenzeller found the reproductive organs developed. 
The colour is reddish or brownish-grey, lighter on the ventral surface. The tops of 
the dorsal papillse are light, in one individual almost whitish. Even the sucking-disks of 
the pedicels are light coloured. The largest processes attain a length of about 15 mm., 
and a breadth at the base of 8 mm. or more, and their arrangement agrees wdth that 
described by von Marenzeller. The small dorsal papillae, scattered among the larger, 
seem to be rather numerous. 
The rather long, slender genital tubes are several times branched, and form two 
bundles not very thick, one on each side of the dorsal mesentery. The Cuvierian organs 
'Seem to be absent. A single Polian vesicle and madreporic canal are present. The 
calcareous ring is peculiar not only in that the ventral interradial pieces are smaller than 
the dorsal, but especially in that the dorsal radial pieces (PI. VIII. fig 2,/) are provided 
with rather considerable posterior prolongations, which, on the contrary, is not the case 
with the ventral radial pieces (PL VIII. fig. 2, g). Thus, when examining only the 
ventral part of the calcareous ring, one cannot get any exact idea of its true conforma- 
tion. Stichopus japonicus, var. typicus, is not the only form that I have seen with such 
an asjmimetrical calcareous ring. 
The calcareous deposits consist of tables alone, but comparatively few of them 
are fully developed, by far the greater part j)resenting themselves under the shape of 
perforated disks with the margin very uneven or spinous, and with no spine or a very 
poorly developed one (PL VIII. fig. 2, d). The largest of these disks measure about 
0'05 mm. in diameter. The rare complete tables are smaller and larger, composed of a 
rounded perforated disk with smooth margin and a spire built up of mostly four rods and 
one or more transverse beams (PL VIII. fig. 2, a, h, c). The spire often terminates in four 
longer or shorter teeth. The larger tables measure about 0’05 mm. in height, and their 
disks have a diameter of 0‘05 mm. There are also to be found tables with a spire com- 
posed of only two rods. The dorsal papillse are strengthened by numerous smooth or 
spinous, curved rods, and, besides, by elongated, bilateral, perforated, button-like plates 
with the holes arranged in two longitudinal rows (PL VIII. fig. 2, e). The pedicels are 
(ZOOL. CHALL. EXP. — PART XXXIX. — 1886.) Q'l 
