OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 265 



arm spines always remain separated by a rather broad interval from 

 the base of the arms outward. 



The tentacle scale is large, elongated, half again as long as broad, 

 with the tip somewhat broadened and provided with two or three 

 small spinules. 



The dorsal surface of the disk is pinkish gray ; the radial shields 

 are studded with small rounded spots of a rather light brownish 

 purple ; some similar, though very much smaller, spots occur on the 

 plates in the radial spaces of the dorsal surface of the disk ; in the 

 interradial spaces these spots are very much broader and may cover 

 the whole surface of the plates. The dorsal surface of the arms is ex- 

 tremely dark in color, a very dark green, almost black ; this colora- 

 tion extends to the whole space included between the two lateral rows 

 of spines, that is to say, to the upper arm plates and to the adjacent 

 portions of the side arm plates, in such a way as to form a very broad 

 band, but the width of this band diminishes somewhat at some dis- 

 tance from the disk. The most projecting part of the dorsal keel is 

 marked by a somewhat lighter and extremely narrow line which is 

 bounded by two darker and also extremely narrow lines ; sometimes 

 this triple line can scarcely be distinguished from the very dark gen- 

 eral coloration of the dorsal surface of the arms. The ventral sur- 

 face of the disk shows a very dark brown coloration in the parts not 

 covered with plates, but the plates themselves are of a pinkish gray. 

 The mouth pieces and the ventral surface of the arms are of this same 

 pinkish gray coloration ; a somewhat darker band brownish in color 

 runs all along this ventral surface on either side and at some distance 

 from the median line, almost following the sides of the under arm 

 plates, and it forms a rounded spot rear the proximal border of each 

 of these plates. 



Affinities and distinctive features. — Ophiothrix signata belongs to 

 the 0. suensoni group and appears to be especially close to 0. viridi- 

 alba Martens ; unfortunately the description which Martens gave of 

 this species is very short, and is not accompanied by figures; it is 

 very difficult, therefore, to form an exact idea of it. However, certain 

 characters attributed by Martens to O. viridi-alba do not agree with 

 those which I find in my species. The radial shields are completely 

 unarmed, the upper arm plates, which are longer than broad, are 

 slightly carinate, and the arm spines number four or five; while 

 in O. signata the radial shields bear a row of club spines along their 

 radial border, the upper arm plates, which are slightly broader than 

 long, are very strongly carinate, and the arm spines are very much 

 more numerous. Regarding the coloration, Martens says that the 

 upper arm plates are " lebhaft griin," while the coloration is so dark 

 in 0. signata that it appears almost black. 



