CLARK: BRITTLE-STARS. 275 



long and .80-.85 mm. wide; they are closely joined except at inner 

 end where a couple of scales intervene. Upper arm-plates twice as 

 wide as long or wider, in contact for their full width or nearly so. 

 Interbrachial areas below covered by scales very similar to those of 

 the upper surface of disk but somewhat finer. Genital slits long but 

 inconspicuous. Oral shields spearhead-shaped with rounded angles, 

 distinctly longer than wide. Adoral plates very small, not meeting 

 in interradii, triangular with inner side concave. Oral plates small. 

 Oral papillae three on each side, the distalmost largest and borne on 

 the adoral plate. First under arm-plate moderately large, not swollen, 

 the proximal side narrowed to a rounded point, the distal side rounded; 

 succeeding plates wider than long, the distal margin concave, the 

 proximal convex but not enough so to make the plate pentagonal; 

 the plates are all broadly in contact but are perfectly flat and not at 

 all swollen. Side arm-plates quite small, low and short; each carries 

 three flattened, blunt subequal arm-spines, about as long as an arm- 

 segment. Tentacle-scales two, one on the under arm-plate, the other 

 on the side arm-plate, but in close contact with each other. Color, 

 in life, disk uniform light gray; arms yellowish white; at intervals 

 of 4-6 segments, one or two upper arm-plates are bright green, and 

 there is also a narrow longitudinal stripe of green running the whole 

 length of the arm but rather faint proximally. In young specimens, 

 the longitudinal stripe is bright orange-red and this may perhaps 

 persist in some adults. Oral surface nearly white, but certain under 

 arm-plates are dusky or (distally) greenish or bright green; these 

 colored plates correspond in position to the colored upper arm-plates. 

 In preserved specimens, the green shades are duller than in life and 

 the orange fades and will probably disappear. 



This is one of the handsomest of the brittle-stars found at the 

 Tortugas, young specimens being particularly fine with their combina- 

 tion of white, green, and orange-red. The smallest specimen is less 

 than three mm. across the disk and the arms do not much exceed 

 twenty mm., but the marginal papillae are relatively larger and more 

 numerous than in the adults. The sharply banded appearance of the 

 arms give this Ophiophragmus a characteristic facies quite different 

 from that of any other member of the genus, which I have seen. 



Ophiophragmus septus. 



Amphiura septa Liitken, 1859. Add. ad hist. Oph., pt. 2, p. 120. 

 Ophiophragmus septus Lyman, 1865. Illus. cat. M. C. Z., no. 1, p. 132. 

 Amphiodia erecta Koehler, 1915. BuU. 84 U. S. N. M., p. 67, pi. 6, fig. 4-7. 



