CLARK: BRITTLE-STARS. 285 



angles slightly rounded; they are as wide as long or wider and are 

 barely in contact. Side arm-plates rather large, scarcely meeting, 

 however, either above or below until beyond the middle of arm; 

 each carries 3 (at base of arm, 4) spines, a little longer than the seg- 

 ment; the lowest is stout at base but tapers somewhat abruptly to a 

 blunt point; the next (second) is much stouter and has a very blunt, 

 almost truncate, more or less prickly tip; the third is much more 

 slender and quite acute; the fourth, when present, is similar to the 

 third but is much smaller. Tentacle-scales 2, large and flat, one on 

 the side arm-plate and the other on the under arm-plate, as usual. 

 Color, in life, pale yellowish with a distinctly greenish tinge, especially 

 on the disk; in the dry specimen the colors are little changed. 



The paratypes (except one very small one) differ markedly from 

 the holotype in color. They are more or less dusky with or without 

 a distinct green tinge, and the arms are variegated to a greater or less 

 degree with dusky and whitish. In four of the paratypes, the primary 

 plates of the disk are very well-marked, so that the upper surface has 

 quite a different appearance from that of the type. The radial shields 

 are also much longer and narrower, being fully 3-4 times as long as 

 wide. These peculiarities may be due to the disks having been re- 

 cently regenerated, and this view is strengthened by the fact that the 

 oral surface and the arms are essentially alike in all the specimens. 

 There is more or less individual diversity in the size and shape of the 

 distal oral papilla, and in some specimens it is scarcely as wide as the 

 proximal two. Such specimens approach Amphiodia and it is natural 

 to consider this species as near the border-line between the two genera. 

 It seems to be nearest, however, to Ainphipholis geminata and A. 

 (jracUlhna, from which species it may be distinguished by the arm- 

 plates and spines. 



Ophiostigma rugosum, sp. nov. 



rugosus = rough, in reference to the upper surface of the disk. 



Plate 3, fig. 6. 



Holotype.— M. C. Z. 3,965. Philippine Islands: Mindoro, Port 

 Galera. June, 1912. L. E. Griffin coll. 



Disk, 5 mm. in diameter; arms about 30 mm. long. Disk covered 

 by an uneven, thick skin in which no scales can be detected; there is 

 evidently calcareous matter in or beneath the skin which serves as 



