OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 87 



surface is very rugose, but it is only in the colored portion that I am 

 able to distinguish under the microscope the little black points men- 

 tioned by the American author. The ventral surface of the disk is 

 olivaceous, lighter than the dorsal surface, with less numerous gran- 

 ules, which do not reach the mouth shields, and with little ilack 

 scattered dots. 



H. L. Clark says that the three or four ventral arm spines are 

 " rough or hooked at the tip." But I notice that the modification 

 is more marked than these words would seem to indicate. These 

 spines are covered with rather strong asperities on the three first 

 arm segments, but beyond the fourth, that is to say almost at the 

 borders of the disk, the asperities which arm the terminal portion 

 of the first spine, and sometimes even of the second, elongate, and 

 one of these develop into a little hyaline hook, which is slightly re- 

 curved and turned toward the mouth (pi. 94, fig. la). A similar 

 modification appears very rapidly on the other ventral spines (fig. 

 15), and behind the terminal hook the dimensions of which pro- 

 gressively increase, there are two or three other smaller teeth on the 

 adoral or proximal side of the spines. On the distal side the asperi- 

 ties are less marked, though they are developed for some little dis- 

 tance toward the extremity of the spines. The spines so modified 

 recall the central spine of the species of OpMothrix; but the trans- 

 formation into a true hook is less marked than in this genus, and the 

 spines always retain the character of spines. The dorsal spines are 

 simply rugose, and their asperities remain very fine and very closely 

 crowded without showing the least tendency to become more de- 

 veloped toward the extremity of the spine (fig. lc). On plate 10, 

 figure 5, I give a photograph of the lateral surface of an arm on 

 which the relative length of the soft areas which separate the side 

 arm plates may be appreciated. 



A true tentacle scale is only found on the arm pores of the second 

 and of the third pairs, and I do not see the least trace of them on 

 those of the fourth pair. 



Notwithstanding these few differences, which are quite secondary 

 in character, my specimen incontestably belongs to the same species 

 as that of H. L. Clark. 



In his memoir of 1917 Matsumoto (p. 110) considers O. leucostic- 

 tum (H. L. Clark) identical with O. scolopendrica (Lyman). I 

 do not dare to give an opinion on this synonymy, for, judging by 

 Lyman's description and figures, there are some rather important 

 differences between them, of which I have spoken above; 0. scolopen- 

 drica does not show the same form of upper and under arm plates 

 nor the incomplete calcification of different parts of the body which 

 are found in O. leucostictum ; furthermore, Lyman does not indicate 



