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BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



points may agree well in others. Few of the specimens answer to 

 Duncan's description of the color, but the majority have the longi- 

 tudinal white stripe on upper side of arm more or less distinct. 

 Greenish, whitish, gray, and brown tints are more common than 

 red in dried specimens. The arms are often banded with light and 

 dark shades. The radial shields are usually bare, but are often 

 partly, and sometimes wholly covered with the more or less trifid 

 stumps. In some specimens there are no spines on the disk, only 

 the trifid stumps; in others the disk spines are more numerous than 

 the stumps, and the latter are occasionally very few. The relative 

 length of the thorns and the base, of the stumps, and the degree to 



FIG. 127. OPHIOTHKIX KOEEANA. X 3. o, FROM ABOVE; b, FROM BELOW; c, SIDE VIEW OF TWO ARM 



JOINTS NEAR DISK. 



which the thorns are united to each other by membrane vary greatly. 

 In some specimens the stumps are practically wanting and the disk 

 spines very long and crowded; these specimens are so different from 

 typical Icoreana that I attempted to separate them as a distinct 

 species but connecting links are too numerous to permit one to 

 follow that course. The arm spines are usually slender and some- 

 what tapering, not rarely almost acicular though rough, but they are 

 sometimes stouter and very blunt; occasionally they are flattened; 

 the lowest forms a hook, as described by Duncan, but this very 

 inconspicuous feature is not at all diagnostic, for the same structure 

 occurs to a greater or less degree in many species of Ophioihrix. 



