102 THE VOYAGE OF H.M.S. CHALLENGER 



Ophiophyllum. 



Ophiophyllum, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, 1878. 



Disk extremely thin and flat, covered with scales and large radial shields, and 

 bordered by a row of plates which are movable and attached by their inner margins. 

 Mouth papillae arranged in a close row ; no tooth papillae ; teeth. Arm spines thin and 

 broad, standing on outer edge of side arm plate. Two genital openings in each inter- 

 brachial space. 



This singular genus has small relationship with any other. The fringe of thin plates 

 is like that found in Podophora among echinoderms. 



Ophiophyllum petilum, Lym. (PL XII. figs. 13-15). 



Ophiophyllum petilum, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, p. 130, pL vii. figs. 

 179-181, 1878. 



Fringe-like border of disk consisting of about a dozen very thin plates in each 

 interbrachial space. One arm spine, which is wide and flat like a plate of the border. 

 No tentacle scale. 



(Type specimen from Station 174.) Diameter of disk 6 mm. Width of arm, without 

 spines, close to the disk 1*2 mm. Six small, short, square, close-set mouth papillae on 

 either side of an angle, and three smaller diamond-shaped at the apex. Mouth shields 

 rather large fan-shaped, with a deep curve without and an angle within ; length to breadth 

 1 : T2. Side mouth shields narrow, bounding the inner angle of the mouth shield ; outer 

 ends square, inner ends tapering and separated. First under arm plate three sided, with 

 a rounded angle inward, lateral sides straight, and outer edge curved ; the rest are small 

 and pentagonal, with an angle inward. Side arm plates broad and thin, meeting below 

 beyond the second under arm plate, and just touching above beyond the third upper arm 

 plate. Midway of the arm, where it is highly arched, they form most of its covering. 

 Basal upper arm plates diamond-shaped ; those beyond become more or less triangular, 

 with a sharp angle inward, and outer edge slightly rounded. Disk flat and very thin, 

 the centre covered with fine, thin, irregular scales ; interbrachial space on margin filled 

 by one large three-sided plate, with an angle inward and outer edge nearly straight. 

 Radial shields large, three-sided, longer than wide, with outer angles slightly rounded, 

 separated their entire length by a cluster of Irregular scales larger than those of the 

 centre ; in the lower interbrachial space are two regular transverse rows of long and 

 narrow plates. Genital scales small, much longer than wide, extending from the outer 

 corners of the mouth shield to the disk margin. On the margin of the disk there is a 

 fringe-like border of long, thin, rounded scales attached only by their inner margins, 

 about twelve to each interbrachial space. Only one arm spine, which is attached to 



