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



Ophiostigma tenue, Ltk., Vid. Mecldel., Jan. 1856, p. 13 ; Addit. ad Hist., part 2, p. 

 131, pi. iii. fig. 9. 



West Coast of Central America. 



Ophiostigma formosa, Ltk., Oph. Nov. Descr., p. 3., pis. i. and ii. figs. 5a, 56, 1872. 

 Formosa. 



Ophiochytra. 

 Ophiochytra, Lym., Anniv. Mem, Bost. Soc. Nat. Hist., 1880. 

 Disk covered with little, overlapping scales, and small radial shields. Teeth ; no tooth 

 papillae. The small short mouth angles support a line of squarish, close-set mouth 

 papillae on each side. Large side arm plates, which meet above and below, and bear on 

 their outer edge small spines, which, however, stand at nearly a right angle to the arm. 

 Two genital openings in each interbrachial space. 



Ophiochytra epigrus, Lym. (PI. XXVIIL figs. 12-14). 



Ophiochytra epigrus, Lym., Anniv. Mem. Bost. Soc. Nat. Hist., pi. il figs. 17-19, 1880. 



Two small peg-like arm spines. One tentacle scale. Very small radial shields, wider 

 than long. 



(Type specimen from Station 276.) Diameter of disk 5 "5 mm. Length of arm 

 about 1 3 mm. Width of arm without spines 1 '2 mm. Teeth small, wide and short, 

 closely soldered to a small and very thin jaw plate. On either side of mouth angle, a 

 close row of three or four flattened, squarish mouth papillag, whereof the outermost is 

 largest and acts as tentacle scale to the second mouth tentacle. Mouth shields small, of 

 a pointed heart-shape, with the angle inward ; length to breadth, 0"8 : 0'6. Side mouth 

 shields long, and extending far beyond the mouth shields, tapering inward where they 

 nearly or quite meet. First under arm plate about as broad as long, with a curved, or 

 slightly angular outer side, and a tapering angle inward ; the plates beyond are axe- 

 shaped, much wider without than within, bounded without by a curve, on the lateral 

 sides by re-entering curves, and within liy an obtuse angle. Side arm plates long and 

 meeting broadly above and below, thickened on their outer edge, but not flaring. Upper 

 arm plates small, with three nearly equal sides, and an angle inward. Disk round, 

 slightly arched, covered above with pretty regular, rounded overlapping scales, two or 

 three in the length of 1 mm. ; and below by larger and more angular scales. Radial 

 shields very small, wider than long, and touching. Genital openings large, extending 

 from mouth shield to margin of disk. Two very short, peg-like arm spines standing on 

 outer edge of sides arm plates, but at nearly a right angle to arm. One oval tentacle 

 scale. 



