OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 405 



convex. The three following plates are large, triangular, as long as 

 broad, with a sharp proximal angle, the sides notched by the tentacle 

 pores, which are rather large, and an almost straight distal border ; 

 they are separated by a narrow interval. The following plates 

 become almost triangular ; they are very much smaller, broader than 

 long, and widely separated. It can not be said that these plates have 

 a strictly triangular shape, for the two lateral borders are usually 

 broken up into two short sides united by a very obtuse angle, and 

 the two proximal sides are slightly concave. 



The side arm plates carry a series of small spines which extend 

 for almost the entire length of their distal border ; these spines are 

 very short, conical, and very closely crowded, and altogether they 

 form a sort of fringe in which there may usually be counted nine 

 spines; but there may be only eight of them, or their number may 

 rise to ten. 



The tentacle pores number three pairs ; those of the first pair are 

 rather large, and they bear on each border three rather small and 

 rounded scales; sometimes the proximal and external border shows 

 only two scales which are a little larger than usual. The pores of 

 the second and of the third pairs in general have only a single 

 proximal scale; sometimes they add two small scales on the distal 

 and internal border. 



The color of the specimen in alcohol is yellowish. 



Affinities and distinctive features. Ophiomusium fimbriatum is 

 very close to O. multispinosum H. L. Clark. The dorsal surface of 

 the disk shows a very similar arrangement of plates, and the mouth 

 papillae and the adoral and oral plates have also the same characters, 

 but the mouth shields have the distal border slightly concave instead 

 of showing a short and broadened lobe. The greatest difference 

 consists in the number of tentacle pores, which in the new species 

 are three pairs only instead of four ; furthermore, these pores appear 

 more developed, and those of the first pair, which are rather elon- 

 gated, have a few scales on each border ; the spines are less numerous 

 than in O. muUispinosum, in which their number varies between 

 twelve and sixteen. Ophiomusium glabrum Liitken and Mortensen, 

 which, according to H. L. Clark, is perhaps identical with O. multi- 

 spinosum, has four pairs of pores furnished with a single scale on 

 each border, and, according to the authors' figure, the pores of the 

 first pair are not larger than those following; the distal border of 

 the mouth shields is slightly convex, and the number of spines varies 

 between seven and eleven. 



In the arrangement of the dorsal plates of the disk and the rela- 

 tive shortness of the genital slits O. fimbriitum also recalls 0. planum 

 Lyman, but it differs from it in the more numerous arm spines, 

 as well as in the form of the mouth shields. 



