322 bulletin: museum of comparative zoology. 



plates, broadly in contact. Side arm-plates small with five or six 

 arm-spines, of which the lowest is very small and the uppermost (of 

 six) is small, smooth and terete; remaining spines rather glassy and 

 thorny, the uppermost or fifth the longest and equalling two -two and a 

 half arm-segments. Tentacle-scale single, sharp, rather flat. Color, 

 dried specimen, disk, dull red, with its spinelets, stumps, and distal 

 tips of radial shields, dirty whitish; ground-color of arms and arm- 

 spines, reddish white; on the upper surface of each arm are two 

 broad, longitudinal stripes of dull black, and on each side of arm, 

 close to the upper ends of the side arm-plates, is a less distinct and 

 more or less interrupted stripe of the same shade; none of the stripes 

 have straight or sharply defined boundaries ; lower surface of disk and 

 arms dull red, with the madreporite and a conspicuous, median, rather 

 broad longitudinal stripe on the under arm-plates, nearly white. 



The paratypes are of particular interest as no two of them agree in 

 color and none is like the holotype. The diversity of the species in 

 that respect is well-shown, and it is both interesting and important 

 to note that the striping of the arms is a constant feature. The most 

 interesting specimen is the smallest; the disk is not quite 3 mm. across 

 and is dull pinkish in color; its stumps and spinelets are much more 

 slender than in the holotype; the arms and arm-spines are nearly 

 white but dorsally on each side is a distinct though very narrow stripe 

 of dull purple and ventrally the under arm-plates are purplish on both 

 sides, leaving a broad white stripe down the middle; it is perfectly 

 obvious that the only difference between this coloration and that of 

 the holotype is that in the latter pigmentation is much heavier. A 

 second specimen, 4 mm. across the disk is perfectly intermediate 

 between the smallest specimen and the holotype not only in coloration 

 but in the spinulation of the disk. A third specimen resembles the 

 holotype in all particulars except that the ground-color is violet instead 

 of reddish and all the oral shields are white. The fourth specimen 

 is in very poor condition and seems to have been bleached; the dark 

 stripes on the upper side of the arms can be detected only with difficulty, 

 but the light stripe on the under arm -plates is perfectly obvious. 



This new Ophiothrix is characterized by the striped arms, which 

 are relatively longer than in 0. trilineata and its allies but much 

 shorter than in the 0. longipeda group ; by the disk-covering, the large 

 upper arm -plates, the small side arm-plates and the few arm -spines. 

 In all these features, it seems to be quite constant and well set off 

 from the other members of the genus. 



