OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 433 



as broad; they are at first in contact, then become separated by a 

 narrow interval. 



The first under arm plate is rather large, triangular, broader than 

 long. The following are very large, pentagonal, with a sharp proxi- 

 mal angle bounded by two short straight sides, and two lateral bor- 

 ders excavated by the tentacle scale which pass over by very rounded 

 angles into the distal side, which is broad and rounded. The proxi- 

 mal angle is truncated on the second plate. These plates are almost 

 as long as broad, and they are in contact as far as the fourth, thence 

 becoming separated by a space which progressively elongates, and 

 becomes simply triangular. 



The side arm plates, which are rather strongly projecting, bear 

 three spines which are short, thick, and subequal, with the surface 

 rugose. 



All the arm plates have their surface covered with rather coarse 

 granules like the plates of the disk. 



The tentacle scale is single, oval, and of medium size. 



The general color of the dorsal surface of the body is rather 

 dark; it is a brownish green, and each of the dorsal plates of the 

 disk shows a large very dark spot, which on the central plates covers 

 almost their entire surface. The upper arm plates also show a 

 similar large spot. The ventral surface is very much lighter, and 

 the plates show similar but very much smaller and less well marked 

 spots. 



Affinities and distinctive features. — This species evidently falls 

 into the genus Ophiozonoida, which H. L. Clark has very recently 

 erected for an ophiuran from New Zealand, Ophiozona picta ('15, 

 p. 340), and the Philippine species is so close to it that I have hesi- 

 tated to separate them. But the differences which I find are not 

 negligible. The dorsal plates of the disk are less numerous and 

 larger than in the New Zealand species, the mouth shields have a 

 slightly different outline and they are a little narrower and more 

 -elongated, and the under arm plates are appreciably larger. The 

 coloration is very different. The dark spots on the large dorsal 

 plates of the disk cover almost the whole surface, as I have de- 

 scribed above; the arms are not at all annulated, but show a large 

 dark spot on each upper arm plate. The coloration is quite other- 

 wise in O. picta, and the spots which the different plates show are 

 of a very much more brilliant color — " dull brownish with a purple 

 tinge," according to H. L. Clark. These spots occur on the small 

 plates of the dorsal surface of the disk and are not confined to the 

 large plates, and they also occur on alternate arm segments, while 

 the upper arm plates of the segments which remain light show a 

 small dark spot. This elegant livery is very different from that of 

 the Philippine specimen, which is very dark on the dorsal surface. 

 55269— 22— Bull. 100 28 



