CLARK: BRITTLE-STARS. 331 



tetragonal, longer than broad, with distal end not much wider than 

 proximal and angles little rounded; they soon become wider than 

 long with distal margin longer and more curved than proximal. They 

 are broadly in contact throughout. Interbrachial areas below covered 

 with a thin and perfectly naked skin. Oral shields diamond-shaped 

 with rounded corners, as wide as long. Adbral plates long and narrow, 

 meeting within; they are much wider at the outer end and the distal 

 angle tends to separate the oral shield from the first side arm-plate. 

 Oral plates very small and difficult to detect. Oral papillae 4 on a 

 side, borne on the adoral plate; the distalmost papilla is very small 

 and is hardly worthy of the designation; the other three are twice 

 as long as wide, flat and pointed. Tooth-papillae 6-10, thick, pointed, 

 rather crowded. First under arm-plate moderately large, wider than 

 long, the distal margin longer and more convex than the proximal; 

 succeeding plates shield-shaped, at first quite angular and longer than 

 wide but finally becoming about as wide as long, with rounded angles; 

 at first the distal margin is deeply concave but this soon becomes 

 scarcely noticeable. Side arm-plates short and high; each carries 

 8 arm -spines, of which the lowest is much the longest; it equals nearly 

 two segments, is slender, cylindrical, distinctly curved and rather 

 obtuse; the next or second spine is similar but shorter; the third is 

 very much shorter, flatter, and straighter; the fourth and fifth are 

 like the third but a little smaller; the sixth is similar but longer and 

 a little wider; the seventh slightly exceeds the sixth and the eighth, 

 the seventh, in both length and width. Tentacle-scales as usual in 

 the genus, 2, the outer small and insignificant, except on the basal 

 joints, the inner long, flat and spine-like and lying diagonally across 

 the lower surface of the arm. Color, in life, little altered by preserva- 

 tion, disk yellowish gray, the radial shields white; arms very pale 

 yellow, banded at intervals of 2-6 segments with reddish brown rings 

 1 or 2 segments wide; upper arm-plates sparsely but regularly spotted 

 along the lateral margins with minute dots of reddish brown. 



The paratypes are in very poor condition, one lacking the disk and 

 the other consisting of only two arms connected by a fragment of 

 the disk. All three specimens were taken in a single dredge-haul on a 

 fine, sandy bottom. Their appearance indicated that this species 

 lives, like so many long-armed amphiurids, buried in the sand. Its 

 habits therefore would seem to be quite different from those of 0. 

 riisei which is a rock- and coral-loving species. While 0. vittata 

 resembles 0. maculata in its arm-spines and coloration of arms, the 

 disk-covering and oral armature are so different the two species will 

 not be confused. 



