l74 



THE YOYAGE OF H.M.S. CHALLENGEE. 



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 

 02')h.iocoma 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, blade-like, grooved scale attached inside its end. 



Species of Ojyhiarihrmn not herein described. 



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

 Archiv, p. 82, 1852. 

 Great Ocean. 



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

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



Ophiocoma pkta, Miill. & Tr., Syst. Ast., p. 102, 1842. 

 Oi^hiura pida, KuU. 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. Eadial 

 shields covered. Teeth and mouth papillfe, and very numerous close-set tooth papillaj, 

 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 oj)enings, beginning 

 outside the mouth shield. 



In general internal structure this genus is similar to OiMocovia, 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 02:)hiom€ixtvx 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 Opliiomastix. 



Disk beset on Iwtli sides with long tliiu spines. Under arm \ QpldfrniaMx nvmdnsu. 

 plates squarish, . . . . . . ) ^ 



Disk with spines as m the preceding. Under arm plates much ) Ophiomastix can/oph ^/Uata. 

 wider than long, . . . . . .J . j . 



Disk closely beset with grains and spines, . . . Ophioin(i>!fix mixta. 



A few spines on upper disk. Upper arm spine not club-shape. 1 ,, i • ,,„./,-. -ijuali- 

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



Two tentacle 

 scales. 



