17(3 THE VOYAGE OF H.M.S. CHALLENGER. 



OiJiliiopteris. 



OpMojyteris, E. A. Smith, Ann. Mag. Nat. Hist., 1877. 



Disk granulated. Radial shields covered. Mouth angle small and short with a few 

 small, spaced mouth papillse. Tooth papillfe very numerous and arranged in a close 

 vertical clump somewhat as in Ophiothrix. Four teeth. Spines smooth and solid ; the 

 upper one having one or two supplementary scale-like spines applied at its base. One 

 tentacle scale. Two genital openings beginning outside the mouth shields. 



For remarks on internal structure, see near the end of Oj^hiocoma. 



Species of Ophiojyteris not herein described. 



Ophiopferis antipodum, E. A. Smith, Ann. Mag. Nat. Hist., p. 305, 1877. 

 New Zealand. 



Op)liiocMton. 



Opldochitoii, Lyni., Bull. Mus. Comi^. Zool., 1878. 



Disk covered with fine, imbricated scales and small radial shields. Numerous sharp 

 mouth papillfe, with teeth but no tooth papillae. Upper and under arm plates about as 

 broad as long, and separating the side arm plates, which project slightly and are rather 

 small. Under plates furnished with a median longitudinal ridge. Arm spines slender and 

 smooth, arranged on the sides of the side arm plates, near the outer edge. Two long 

 genital openings in each interbrachial space. 



The genus is allied to the true Ophiarachna, which, however, has a granulated disk. 



Ophiochiton fastigatus, Lym. (PL XXIV. figs. 13-15). 



Ophioclnto7i fastigatus, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, p. 132, pi. vii. figs. 182, 

 183, 1878. 



Four slender, .smooth, tapering, blunt arm spines. Scaling of disk very fine, with a 

 few larger rounded plates. Radial shields small and separated. About thirteen mouth 

 papillse to each angle. 



(Type .specimen from Station 232). — Diameter of disk 20 mm. Width of arm, 

 without spines, close to the disk 2 '8 mm. Five or six sharp-pointed papillae on each side 

 of an angle, and one shorter and more rounded at the apex. Mouth shields much broader 

 than long, with lateral corners rounded, a peak within and a lobe without ; length to 

 breadth, 2'3 : 3. Side mouth shields very narrow, broader without than within, where 

 they meet. First under arm plate very small, triangular ; the other plates are four sided, 

 with outer and inner edges nearly .straight, and deep re-entering curves on the lateral 



