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 LIII. fig. 4). On Loth 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 \vdder 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 sufiiciently characteristic to 

 indicate that it belongs to a difi"erent 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 Mctacrmus nodosns (PL 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 nodosus, 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' S., long. 132° 14' E. ; 140 fathoms ; blue mud. A stem-fragment only. 



Family Comatulijd^, d'Orbigny, 1852. 

 Genus Thaumatocrinus, P. H. Carpenter, 1883. 



TliaumatocriHus, P. H. Carpenter, Pliil. Trans., part iii., 1883, p. 919, pi. 71. 



Definition. — -Calyx composed of a centro-dorsal, basals, radials, and primary inter- 

 radials, the latter resting on the basals and so separating the radials laterally. That 

 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, i.e., provided with a 

 centro-dorsal plate or cirrus-bearing top stem-joint which separates it from the remainder 



