78 
THE YOYAGE OF H.M.S. CHALLENGER. 
(PI. VI. fig. 8a) are to be found with the inner and outer surfaces knobbed or spinous. 
These cups are built up of an x -shaped central rod, with the branched arms partly con- 
nected so as to form a knobbed or spinous continuous rim, partly free and devoid of any 
complete rim, a condition which seems to be the most usual. The diameter of the cups 
measures OTO mm. With the exception of these cups, one finds in the perisome small, regu- 
larly formed, thick, robust buttons (PI. VI. fig. 8h) with large, rounded knobs and usually 
four holes, and, moreover, other numerous more or less regular or symmetrical buttons of 
a more dehcate conformation, and provided with a greater number of holes and knobs. 
A whole series of transitional forms between the two extremes of buttons are to be seen. 
The scales do not reach any more considerable size. The pedicels are strengthened by 
rather large, robust and broad, crowded, rod-like plates, and also by terminal plates and 
buttons. Even the “papillae” are supported by plates. On treating a piece of the 
integument with a solution of potash, one finds here and there larger and smaller almost 
smooth perforated plates, but these are probably derived from the pedicels or processes. Any 
more obvious imbrication of the scales in the anal portion of the body is not to be observed. 
Colochirus violaceus, n. sp. (PL XIII. figs. 1, 2 ; PI. V. fig. 4). 
Body cucumiform, equally rounded anteriorly and posteriorly. Tentacles ten (?), 
only six being left. Pedicels arranged in three distinct series along the ventral 
surface, each series composed of four to five rows. The series decrease in breadth 
towards the extremities of the body, where the pedicels are represented by “ papillse.” 
The whole dorsal surface is covered with small scattered conical papillae, those on the 
ambulacra being slightly larger than those on the interambulacra, which are minute. 
Even the ventral surface carries minute papillae on its interambulacra. The oral opening 
is surrounded by five groups of rather large conical papillae, each group being composed 
of two or three papdlae united at their bases. The anus is surrounded by five very large 
and rough calcareous teeth. The perisome is thick, leathery, and remarkable on account 
of its scarcity in deposits, which consist of small, very irregular, smooth plates usually 
perforated by one to four, seldom more, holes ; among these deposits, small rod-hke or 
X -shaped ones are to be found. Excepting terminal plates and a few perforated, trans- 
verse rods, no deposits occur in the pedicels. The papUlse are provided with a few 
perforated rods, and are entirely devoid of or possess only very small terminal plates ; . 
moreover, the larger papillae seem to be strengthened by large irregularly reticulated 
plates composed of several layers. Colour in alcohol, light violet, here and there inclinmg 
to yellowish and bluish ; the papillae and anal teeth are lighter, the former mostly 
resembling white or yellowish spots. Length about 190 mm. 
Habitat . — Station 203, October 31, 1874; lat. 11° 6' N., long. 123° 9' E. ; depth, 
20 fathoms ; mud ; a single specimen. 
