RECENT OPHIURANS. 295 



numerous, a mill imeter long or more, slender but not acicular. No radial 

 shields are visible. Upper arm-plates diamond-shaped, nearly twice as wide as 

 long, more or less in contact. Interbrachial areas below show the fine scaUng 

 much more clearly than the disk and carry few spines. Oral shields longer than 

 wide, octagonal with corners rounded, especially proximally ; disto-lateral margins 

 each with a low conical spinelet. Adoral plates trigonal, the side adjoining oral 

 shield much the longest. Oral papillae 4-5, on a side, the two distalmost largest. 

 Tooth-papiUae small and numerous, 15-18 on each jaw tip. Under arm-plates 

 much wider than long, broadly in contact; the true outlines are obscured by 

 the peculiar coloration; they are broadly octagonal with distal corners rounded. 

 Side arm-plates not prominent; each carries a series of 3 or 4 spines, the upper- 

 most longest; when there are 4 the uppermost may exceed 5 joints and is fre- 

 quently very thick and often clavate. These stout spines occur at intervals of 

 2-6 joints and alternate on the two sides of the arm. Tentacle-scales 2, rather 

 large, fiat and rounded but longer than wide. Color (dried) : — disk, brownish 

 gray with numerous spots and small blotches of blackish; disk spines gray with 

 two or three riugs of hght brown; upper arm-plates and distal half of side arm- 

 plates gray; proximal half of side arm-plates blackish, in marked contrast; 

 stout arm-spines dark gray; other arm-spines light gray annulated with brown- 

 ish; interbrachial areas below gray with blackish spots; oral shields gray, but a 

 conspicuous blackish band across the surface of the jaw includes the proximal 

 end; under arm-plates pale gray but their distal margins on each side are invaded 

 by the black of the side arm-plates, obscuring their real outlines; tentacle-scales 

 very light. 



HoLOTYPE (M. C. Z. 3775) and 40 pabatypes (M. C. Z. 3373, 3374, 3862). 

 Torres Strait: Murray Islands, Mer. October, 1913. Carnegie Exp. 1913. 

 H. L. Clark coll. 



This is one of the common brittle-stars in the dead coral on the southeast- 

 ern reef-flat at Mer. It occurs in company with 0. caryophyllata and the much 

 rarer 0. asperula. Although at first glance very similar to caryophyllata, com- 

 parison of two specimens shows that they are perfectly distinct. The shape 

 of the upper arm-plates is an important feature, in which they differ constantly, 

 while the difference in color-pattern is very striking and surprisingly constant. 

 In scores of specimens examined, of widely diverse ages and sizes, I never saw 

 a specimen which could be considered an intermediate between the two species. 

 These ophiurans are very active, keeping constantly in among the coral branches 

 (hence the name) and never occurring on the sand, under coral fragments, where 



