REPORT ON THE OPHIUROIDEA. 167 



Colour in alcohol, pale greenish-grey ; arms lighter. 



Station 276. — September 16, 1875; near Low Archipelago; lat. 13° 28 S., long. 

 149° 30' W. ; 2350 fathoms ; red clay. 



This solitary representative is highly interesting as almost the only deep-sea Ophiuran 

 found by the " Challenger " in the immense distance between the Sandwich Islands and 

 the south-west coast of South America. 



Ophiocentrus. 



Ophiocentrus, Ljn., Oph. Viv. Of. Kong. Akad., 1866. 



Disk covered by a soft skin, except a portion of radial shields, and set with short 

 spines. Four mouth papillae to each angle, whereof two are very thick and standing under 

 the teeth ; and two minute ones, standing at the outer corners. Arms long (ten times 

 diameter of disk), with very narrow upper arm plates, which barely separate the two 

 rows of numerous (seven) rough arm spines. Two genital openings in each interbrachial 

 space. 



Species of Op>hiocentrus not herein described. 



Ophiocentrus aculeatus, Ljn., Oph. Viv. Of. Kong. Akad., p. 321, 1866. 

 Between Batavia and Singapore. 



Ophiocoma. 

 Ophiocoma, Agas., Mem. Soc. Sci. Nat. Neuchatel, 1835. 



Disk granulated. Radial shields covered. Teeth, and mouth papillae, and very 

 numerous close-set tooth papillae, arranged in a vertical clump. Spines, usually from 

 four to six ; smooth, solid (except in Ophiocoma nigra). One or two tentacle scales. 

 Two genital openings, beginning outside the mouth shield. 



Under the disk granulation is a smooth scale coat, very fine toward the centre ; coarser 

 towards the border, where runs a marginal belt of much larger scales connecting the outer 

 ends of the radial shields (PI. XLII. fig. 9, I), which are oblong, with protruding corners. 

 They are continued inward by a broad stripe of large, strongly overlapping scales, a 

 feature nowhere so developed as in this genus. The genital plate is like a thick blade, 

 with rounded edges and a slightly clubbed head for articulating with the radial shields, 

 and to whose side is attached a short, thin blade-Uke genital scale (fig. 12, l,n,o). As 

 seen from above, the arm bones are of very simple structure, being short, with thin, flat, 

 plain-edged wings, and destitute of any forward projections from the upper surface. 

 Their outer and inner faces are of a high type, having the articulating peg and other 

 details well marked (figs. 10, 11). The mouth angles are compactly built and of moderate 

 size, without flaring wings, or high crests, thus differing greatly from Ophiophrag- 



