352 THE VOYAGE OF H.M.S. CHALLENGER. 



wide sockets which take up their whole height and encroach considerably both ou 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. Eadials 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. Eight 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 joints 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 aljove the enlarged basal joints, wlide 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 Brachial ambulacra partially withdrawn into the arm-groove, and supported by 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 diff'erentiated tUl near the ends of the 

 pinnules. 



Colour when fresh — the stems almost white, and the crowns light yellow or light 

 reddish-orange (Moseley) ; in spirit, white, with traces of light l^roM'n. 



Localitij. — Station 192, September 26, 1874 ; in the Arafura Sea, off the Ki Islands ; 

 lat. 5° 49' S., long. 132° 14' E. ; 140 fathoms ; blue mud. Two large specimens, one of 

 which has lost all its arms, and one smaller varietal form. 



Remarhs. — This fine species is readily distinguished from Metacrinus murrayi by its 

 flat ungrooved stem (PL XLI. fig. 5), with shorter internodes and more markedly incised 

 infra-nodal joints (PI. 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 resemljles Metacrinus nohilis in having a flat ungrooved stem 

 (PI. 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 Metaxrinus superbus has many more cirrus-joints and its arm -bases uneven, 

 owing to the thickness of the proximal and distal edges of the joints. 



