OPHIURANS OF THE PHILIPPINE AND ADJACENT WATEES. 231 



would permit of distinguishing it from 0. expedita. Generally 

 speaking, the radial shields of this last named species are relatively 

 somewhat more elongated ; they occur in the form of a very flattened 

 isosceles triangle of which the base is turned from the radial side and 

 of which the very rounded apex is situated almost in the middle of 

 its length. This apex is thus a little further from the periphery of 

 the disk than in 0. rhabdoid, but I do not believe that this character, 

 which is not very reliable, can be utilized to separate these two species 

 of Ophiothrix. 



In the largest of the specimens collected by the Albatross the gen- 

 eral coloration is bluish gray. The dorsal surface of the disk is a 

 rather dark gray, and the radial shields are lighter with a bluish 

 tinge. The arms show, on the dorsal surface, three longitudinal light 

 lines, which, in the alcoholic specimen, are white and stand out clearly 

 from the blue background. The white bands are not absolutely con- 

 tinuous, and they are interrupted at the line of separation of the suc- 

 cessive upper arm plates; the median band is a little broader than 

 the others. On the other specimen the three lines are narrower, while 

 the two blue bands which border the median white band on either 

 side are more marked and broader, and their outlines are a little 

 clearer. Beside these very constant lines, there are on both speci- 

 mens indications of rings alternately a little lighter and a little 

 darker. A white band runs all along the ventral median line of the 

 arms and is bordered on either side by a blue line beyond which is 

 found on each segment an elongated white spot. On the ventral sur- 

 face of the arms also traces of rings are to be seen, and in the large 

 specimen these annulations are alternately blue and reddish, the blue 

 portions being slightly washed with white ; furthermore, in this same 

 individual, the arm spines are slightly washed with red at the base, 

 and this red coloration shows itself especially in the distal half of 

 the arms. On the smaller individual the white and blue lines of the 

 ventral surface of the arms are better marked than in the other, the 

 blue color being somewhat more intense, but it is not mixed with red 

 and the annulations are alternately blue and white. 



H. L. Clark does not seem to have proposed O. rhabdota without a 

 certain amount of hesitation, and according to him this species is only 

 distinguished from various forms of the 0. lonrjipeda group by its 

 coloration and especially by the three light lines which run along the 

 whole length of the dorsal surface of the arms. These lines, which 

 are white in alcoholic specimens, are yellowish in the living animal. 

 The general coloration of the specimens is not indicated by Clark in 

 his description, but he informs me by letter that that color was blue. 

 The color scheme which I find in my specimen is thus very similar to 

 that of the specimen studied by H. L. Clark. 



