174 



THE VOYAGE OF H.M.S. CHALLENGER. 



there may be found, however, minute, loose, perforated lime scales, and its under side is 

 supported by radial shields, and by radiating and marginal scale lines similar to those of 

 Ophiocoma but much smaller. The resemblance is carried out in the peristomial plate 

 and the arm bones. The genital plate has a long, clubbed, articulating head, with a thin, 

 long, hladt-like, grooved scale attached inside its end. 



Species of Ophiartkrum not herein described. 



Ophiarth rum elegans, Pet., Monatab. Kong. Akad. Berlin, 1851, p. 464 ; Wieg. 

 Archiv, p. 82, 1852. 

 Great Ocean. 



Ophiarthrmm pictum, Lym., Bull. Mus. Comp. Zool., vol. iii., part 10, p. 225, 

 pi. vii. figs. 2-4, 1874. 



Ophiocoma picta, Mull. & Tr., Syst. Ast, p. 102, 1842. 

 Ophiura pida, Kuhl. u. V. Hasselt., MS. 



Pelews ; Philippines ; Java. 



Ophiomastix. 

 Ophiomastix, Mull. & Tr., Syst. Ast., 1842. 



Disk nearly smooth or set with small spines, or with spines and grains. Badial 

 shields covered. Teeth and mouth papillae, and very numerous close-set tooth papilla?, 

 arranged in a vertical clump. Arm spines few (three to four), smooth, solid ; the upper 

 one being usually club-ended and more or less clavate. Two genital openings, beginning 

 outside the mouth shield. 



In general internal structure this genus is similar to Ophiocoma, except that the 

 radial shields are proportionately larger, the wings of the mouth frames more approached 

 in the interbrachial space, and the genital plate more rounded and longer. As to scaling 

 the disk varies much. Thus, in Ophiomastix venosa, the scales are minute and thin (nine 

 in the length of 1 mm. at centre of disk), while Ophiomastix annulosa has them larger 

 and lumpy (two to three in 1 mm.). 



Table of Species of Ophiomastix. 



Disk beset ou both sides with long thin spines. Under arm ) OMomastlx annulosa , 

 plates squarish, . . . . . . ) 



Disk with spines as in the preceding. Under arm plates much ) 0phiomaslix< . anjophy ii ata . 

 wider than long, . . . . . -I 



Disk closely beset with grains and spines, . . . Ophiomastix mixta. 



A few spines on upper disk Upper arm spine not club-shape. ) hiomasilx janu „,; y . 

 One tentacle scale much smaller than the other, . . ) 



Two tentacle 

 scales. 



