EEPORT OX THE HOLOTHTJEIOIDEA. 
77 
flat, and made up of a central x -shaped rod with the arms connected so as to form a 
complete knobbed ring. In most cases a branched or unbranched rod, or an incomplete 
network covers the concave side of the cups. The cups are rounded or oval, with a 
diameter of about 0‘08 mm. The buttons (PI. YI. fig. 126) are very solid, rounded or 
oval, with in most instances four holes and very large knobs ; they are somewhat larger 
than the cups. A few buttons (PI. VI. fig. 12c) are almost smooth without knobs. 
The supporting rods of the ambulacral appendages are usually perforated in each end 
and in the enlarged middle. 
Colochirus inornatus, von Marenzeller, 1881 (PI. VI. fig. 8). 
Habitat . — Japan ; depth, 8 to 50 fathoms ; ten specimens. 
AU the specimens are highly contracted, with the tentacles retracted within the body, 
which presents a fusiform appearance. The mouth is closed by five valvular projections, 
and is in most of the individuals bent upwards. The perisome is rather hard and 
inflexible. The anal portion of the bod)^ is much more tapered and distinctly turned 
upwards. The anus is surrounded by five very minute teeth. The two ventral are 
much smaller than the eight remaining tentacles. All the ambulacral appendages, even 
the dorsal ones, are completely retractile, and distributed all over the body, whereby the 
surface of the latter accj^uires a punctated or finely pitted aspect. No dorsal processes or 
elevations of the body-wall, which are so characteristic of most of the representatives of 
the genus Colochirus, are visible. Only in one sj^ecimen does the dorsal surface show 
traces of some minute elevations. 
The pedicels, which are marked out from the remaining minute ambulacral appendages 
or “ papillse ” by a larger and more distinct sucking-disk, seem to be arranged in three 
longitudinal ventral series. Each series is broadest at its middle, and is there composed 
of about five pedicels in breadth, but it decreases towards the extremities, where the pedicels 
finally form a double row. Even the ventral narrow interambulacra are occupied by 
some scattered “ papiUse ” and pedicels, the three series being not quite distinctly marked. 
The “ papillse ” are closely crowded all over the dorsal surface and over the anterior and 
posterior parts of the ventral surface, while they, on the contrary, are very thinly 
scattered on the middle of the ventral interambulacra. 
The ventral surface is light, the dorsal, on the contrary, darker, with light spots at 
each papilla. A single madreporic canal and Polian vesicle are present. The three ventral 
pieces of the calcareous ring are considerably narrower than the rest. The ring is always 
devoid of any posterior processes. The retractor muscles are attached to the middle of 
the body. 
The deposits present themselves under several different kinds. In the exterior layer 
of the perisome numerous irregular, reticulate, more or less complete, almost fiat cups 
