370 THE VOYAGE OF H.M.S. CHALLENGER. 
joints (Pl. LIII. fig. 5); so that their re-entering angles are deeper than those of the 
remaining internodal joints (Pl. LUI. fig. 4). On both of these, but especially on the 
infra-nodal (fig. 5), the single tubercles at the sides of the joint are more or less double, 
and enlarged into a horizontal ridge. A peculiarity of somewhat the same kind occurs 
in Metacrinus costatus (Pl. XLIX. fig. 3). 
The cirri are about 35 mm. long, and closely resemble those of other species of the 
genus. They consist of some forty uniformly squarish joints, the basal ones of which are 
not much wider than their successors, though projecting a little beyond them on the 
dorsal side. There is no trace of interarticular pores, so that this fragment cannot have 
come from near the top of the stem. 
Thus, then, the peculiarities of this stem-fragment are sufficiently characteristic to 
indicate that it belongs to a different species of Metacrinus from any of those described 
above. In the prominence of the angles of the nodal joints, and in the presence of 
tubercles along the sides of the internodes, it resembles Metacrinus nodosus (P1. LI. fig. 8). 
But in the sharpness of the ridges formed by the angles of the internodes it approaches 
Metacrinus angulatus (Pl. XXXIX. figs. 3, 11) and Metacrinus costatus (Pl. XLIX. 
figs. 1, 2). As the composition of its calyx is unknown, no place can be assigned to 
Metacrinus tuberosus in the tabular scheme of the genus. If there be four radials it 
would come near Metacrinus angulatus, though the internodes are shorter than in this 
type; but if the number of radials be six, its place would be next to Metacrinus costatus 
and Metacrinus noddsus, both of which it resembles in the length of its internodes. 
Clinging to this stem by its long arms was the pluteus-larva of an Ophiurid, with 
three arm plates beyond the disk. 
Locality.—Station 192, September 26, 1874; in the Arafura Sea, near the Ki Islands; 
lat. 5° 49’ 8., long. 182° 14’ E.; 140 fathoms; blue mud. A stem-fragment only. 
Family ComatuLip&, d’Orbigny, 1852. 
Genus Thaumatocrinus, P. H. Carpenter, 1883. 
Thaumatocrinus, P. H. Carpenter, Phil, Trans., part iii, 1883, p. 919, pl. 71. 
Definition. 
radials, the latter resting on the basals and so separating the radials laterally. That 
Calyx composed of a centro-dorsal, basals, radials, and primary inter- 
on the anal side bears a short jointed appendage. Mouth central, and protected 
by five large oral plates which occupy the greater part of the disk, and are separated 
from the calyx interradials by two or three rows of small irregular plates. Five arms 
only. 
Remarks.—Although this very singular genus is a true Comatula, 1.e., provided with a 
centro-dorsal plate or cirrus-bearing top stem-joint which separates it from the remainder 
