﻿MARSHALL ISLANDS ECHINODERMS — CLARK 297 



Bikini Atoll ; 30-75 feet ; August 15, 1947. One specimen, U.S.N.M. 

 No. E. 7322. 



Notes. — In the last-mentioned specimen (E. 7322) the stellate disk 

 is 13 mm. in diameter and the arms are 70 mm. long. The disk is 

 thickly covered with short sharp spinules. There are two tentacle 

 scales on the first four or six pores. The arm spines are usually three, 

 sometimes four; the enlarged uppermost arm spines are 5 mm. 

 long, usually slender, occasionally thickened. The color (as in E. 

 7324) is olive-brown with the arms obscurely banded. 



Specimen No. E. 7323 has the disk 9 mm. in diameter and the 

 arms 50 mm. long. The disk is thickly beset with very small sharp 

 spinules. There are two tentacle scales on the first three, sometimes 

 four, pores. The color is uniform olive-brown, the spines lighter. 



Specimen No. E. 7326 has the disk 5 mm. in diameter, and beset with 

 scattered sharp spinelets. There are two tentacle scales on the first two 

 or three pores. There are three arm spines. This specimen agrees 

 well with the type as described and figured by Dr. H. L. Clark. 



Dr. Johnson's specimen (No. E. 7624) has the disk 8 mm. in diameter 

 and the arms 50 mm. long. The disk is rather thickly beset with 

 short spines. The arm spines are usually three, occasionally two. 



OPHIOMASTIX SEXRADIATA, new species 



Description. — The disk is 3 mm. in diameter and the six arms are 

 14 mm. long. The disk is covered with small imbricating scales and 

 studded with numerous short stout conical spinelets resembling those 

 on the disk of Ophiocomella clippertoni. 



The general structure is similar to that of 0. clippertoni., but there 

 are only three arm spines — four on the first three or four side arm 

 plates beyond the disk — and the uppermost arm spine is from half 

 again to twice as long as the others, slender and tapering gradually 

 to a sharp tip ; near the arm bases it may be considerably longer than 

 an arm segment. The middle spine is shorter, but usually stouter. 

 The lowest spine is about as long as the middle spine, and usually 

 somewhat more slender. 



The disk is light brown, the spinules white. The upper arm plates 

 are light brown with a narrow white border and a narrow white curved 

 band extending across the plates from the spines on one side to those 

 on the other. The under arm plates are light brown with a narrow 

 distal white border. The oral and adoral shields have a dark center 

 and broad white borders. 



In two of the specimens all six arms are of the same size. In the 

 remainder, three of the arms are much smaller than the others, in- 

 dicating autotomous division. 



Locality. — Bikini Atoll ; in the lagoon ; Morrison, August 26, 1947. 

 Four specimens, U.S.N.M. Nos. E. 7359 (type) , E. 7360. 



