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



surmounted by a disk divided into symmetrical radiating flutings, and with a slight bulb 

 at the base articulated to a little mamelon. They are glassy and translucent, and naturally 

 are enveloped in a skin bag which, however, is easily stripped off, leaving them free, as 

 shown in the figures. They are found on all the outer joints, to the tip of arm. The 

 tentacles are long, smooth, and translucent. The second mouth tentacle has four flat 

 scales similar to mouth papillae. The next two pairs have each two smaller scales, one on 

 the side arm plate, the other on the under arm plate. Each pore beyond has one long, 

 spinedike scale on its inner edge. 



Station 296. — November 9, 1875 ; south-west of Juan Fernandez ; lat. 38° 6' S., 

 long. 88° 2' W. ; 1825 fathoms; red clay. 



Ophiomyces. 

 Ophiomyces, Lym., Bull. Mus. Comp. Zool., vol. i., part 10, 1869. 



Teeth ; no tooth papilla? ; numerous wide, flat mouth papillae, which are turned 

 downwards and outwards, and arranged in two or more imbricated rows, covering the 

 whole mouth angle. Side arm plates large, and meeting above. Disk finely scaled, 

 without radial shields. Arm spines short and numerous (6-12), within the disk shorter, 

 stouter, and of a different character from those of the joints further out. 



This singular genus stands quite by itself, unless we compare its curious mouth 

 papilla? with the spatuladike tentacle scales of Ophiopsila. All the specimens I have 

 seen had a tendency to raise the arms above the disk, vertically ; which shows that the 

 muscular tension must have some peculiar proportion. 



In the absence of radial shields, it differs from all others, and its general structure, 

 without and within, shows additional peculiarities. The genital plate, thin, wide, and 

 long (PI. XLIV. fig. 7, 6), curves over the top of the arm, and has a thin genital 

 scale of similar character (fig. 6, no). The arm bones, within the disk, have large 

 thin wings without marginal grooves. Their outer face is peculiar in having no articu- 

 lating peg (fig. 8), though the inner face is furnished with a large umbo (fig. 9, 1). The 

 jaws and mouth frames (fig. 7 c,f) are of an elegant shape, and curiously twisted. 

 I did not observe any peristomial plate. 



The Plate XLIV. figs. 6-9. 



Ophiomyces spathifer, Lym. (PI. XIX. figs. 10-12). 



Ophiomyces spathifer, Lym., Lull. Mus. Comp. Zool., vol. vi., part 2, p. 47, pi. xiv. figs. 

 386-388", 1879. 



Outer mouth papilla? large and paddle shaped. One flat, rounded tentacle scale. 

 Ten flattened arm spines of various shapes, whereof the two lowest are borne on the under 

 arm plate. 



