352 THE VOYAGE OF H.M.S. CHALLENGER. 
wide sockets which take up their whole height and encroach considerably both on infra- 
nodal and on supra-nodal joints. The cirri have about forty-five tolerably uniform joints, 
and are longest between the twelfth and fourteenth nodes. The interarticular pores end 
at the tenth node. 
Basals prominent, with slight downward extensions. Radials four, rather strongly 
convex, the second a syzygy. Generally four, and sometimes five divisions of the rays, 
giving seventy arms or more. These have from one hundred to one hundred and twenty 
joints beyond the last axillary, and are smooth at the base; but their middle and outer 
portions are markedly serrate in the medio-dorsal line. Primary arms usually of five 
distichal joints, one or sometimes two of which are syzygial. Hight or nine palmars in 
the secondary arms, the second or third of which is a syzygy. Tertiaries of twelve to 
twenty joints (usually about fifteen), with the third a syzygy. In a few cases there 
is another division after about twenty joimts more. There is generally a syzygy in the 
third brachial of the free arm ; another between the twelfth and thirty-seventh brachials, © 
and others at intervals of four to thirteen joints. 
The pinnules on the radials and lower distichals are all very long and much com- 
pressed above the enlarged basal joints, while their terminal portions have a serrate 
dorsal edge. The following pinnules, as far as the tertiary axillaries, have wide 
and somewhat prismatic basal joints like those lower down on the rays, but with more 
curved sides, and consisting of more uniform joints, the dorsal edges of which project 
forwards. 
Disk rather closely plated, especially in the anal interradius and along the ambulacra. 
Brachial ambulacra partially withdrawn into the arm-groove, and supported by 
irregularly shaped plates. Side plates not differentiated till near the ends of the 
pinnules. 
Colour when fresh—the stems almost white, and the crowns light yellow or lght 
reddish-orange (Moseley) ; in spirit, white, with traces of ight brown. 
Locality. —Station 192, September 26, 1874; in the Arafura Sea, off the Ki Islands ; 
lat. 5° 49’ §., long. 132° 14’ E.; 140 fathoms; blue mud. Two large specimens, one of 
which has lost all its arms, and one smaller varietal form. 
Remarks.—This fine species is readily distinguished from Metacrinus murray: by its 
flat ungrooved stem (Pl. XLI. fig. 5), with shorter internodes and more markedly incised 
infra-nodal joints (Pl. XLIII. fig. 1). The primary arms are generally longer than in 
that type, and the extremities of the arms and pinnules more serrate. Metacrinus 
varians, Which resembles Metacrinus nobilis in having a flat ungrooved stem 
(Pl. XLVII. figs. 6, 8), is altogether a smaller type with shorter internodes and no 
axillaries after the palmars, so that the number of arms does not exceed forty; while 
the large Metacrinus superbus has many more cirrus-joints and its arm-bases uneven, 
owing to the thickness of the proximal and distal edges of the joints, 
