REPORT ON THE OPHIUROIDEA. 235 



Ophiambix aculeatus, Lym. (PI. XXVII. figs. 10-12). 



Ophiambix aculeatus, Lym., Anniv. Mem. Bost. Soc. Nat. Hist., pi. ii. figs. 29-31, 1880. 



On upper side of disk and arms, sharp grains, which increase to short spines on 

 margin. Interbrachial spaces below delicately scaled. Three sharp arm spines. 



Diameter of disk 5 mm. Width of arm without spines l - 5 mm. The rather small 

 jaws, which are separated at their outer ends, bear each three or four small, sharp, 

 translucent papilla), while the apex is occupied by the lowest tooth, which is peg-shaped 

 and much larger than the papillae. Mouth shields very small, of a transverse oval 

 shape, with a slight peak within. Side mouth shields short and small, tapering at each 

 end, and wedged between outer ends of jaws. First under arm plate nearly as large as 

 those beyond, somewhat longer than broad, bounded within by an obtuse angle, without 

 by a gentle curve, and, on the lateral sides, by re-entering curves. Length to breadth of 

 fourth plate, 0"6 : - 5. The wide space on either side of the under arm plates is occupied 

 partly by the very large tentacle sockets, and partly by the side arm plates which make 

 narrow partitions between the tentacles, and then enlarge into a strong but very low 

 spine crest. Upper surface of arm covered by skin, and evenly set with sharp, conical 

 grains, about eight in the length of 1 mm. Disk much flattened, and somewhat puffed 

 in the interbrachial spaces ; evenly set above with sharp conical grains, which are similar 

 to those of the arm, and which are continued as minute conical spines, over the margin. 

 Interbrachial spaces below destitute of spines and covered by a thin, delicate scaling. 

 No radial shields are externally visible. Genital openings large, extending from outer 

 corner of mouth shield to margin of disk. The extremely flattened arm bears, on either 

 side, three translucent, hollow, slightly flattened, sharp, tapering arm spines, whereof 

 the two upper are as long as two joints, and the lowest about two-thirds as long. Three 

 or four short, sharp, spine like tentacle scales, standing on the margin of the very large 

 pores, from which protrude simple club ended tentacles. 



Colour in alcohol, straw. 



Station 175.— August 12, 1874 ; near Fiji Islands; lat. 19° 2' S., long. 177° 10' E. ; 

 1350 fathoms; red clay. 



OpMosdasma. 



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



Disk covered with thick soft skin, finely granulated. Arms very slender and 

 knotted, with lower and side plates imperfectly calcified, and no upper plates. Mouth 

 papillae and teeth represented by a bunch of spines, or thorns, at apex of jaw. Arm 

 spines few (3), small and short. Two large genital openings in each interbrachial space. 



A singular genus, which, by its disk covered with soft skin and lack of upper arm 



