CLARK: BRITTLE-STARS. 311 



Carolina to Brazil. Full-grown adults are easily distinguished not 

 only by the size, the maximum for the genus (disk 10-15 mm. across), 

 but by the very dark color which in preserved material may be nearly 

 black. There is no one character by which the species can be cer- 

 tainly distinguished from 0. savignyi but the upper arm -plates usually 

 answer the purpose. As I have never taken a specimen either in 

 Bermuda, Jamaica, or Tobago, which could be referred to 0. niuUeri, I 

 have long been, and still am, in doubt as to the real status of the 

 species. But, it must be admitted, I have never found a specimen of 

 0. samgnyi nearly so large or so dark colored as adult 0. miilleri. 

 At the Tortugas in June, 1917, we dredged a few specimens which 

 seem to belong to this species. The largest, which is certainly not 

 0. savignyi, is 7 mm. across the disk and has arms 50 mm. long. The 

 color in life was very striking, utterly different from any other Ophiac- 

 tis I have seen alive; the disk was gray at center but, becoming 

 gradually rusty red on the margin, was bright pinkish red in the 

 interbrachial areas below; interradially above it was variegated with 

 black and white; oral surface white with a reddish tinge; upper 

 surface of arms buff, variegated with black, light, and dark brown and 

 white so as to appear indistinctly banded; upper surface of arm -spines 

 like upper arm-plates. In the preserved specimen the red and brown 

 shades have disappeared and there is an evident greenish tinge. 



Ophiactis gymnochora. 



H. L. Clark, 1911. Bull. 75 U. S. N. M., p. 139, fig. 54. 



Although this species, taken at Tanegasima, Japan, is superficially 

 very different from 0. savignyi, it is quite possibly only a variety 

 of that species. The upper arm-plates have the swollen, slightly 

 notched appearance characteristic of 0. savignyi, indicated to at least 

 some degree. 



Ophiactis mac-ulosa. 



Von Martens, 1870. Arch. f. naturg., 36, 1, p. 248. H. L. Clark, 1915. 

 Mem. M. C. Z., 25, pi. 11, fig. 3, 4. 



In the Memoir above quoted, I have listed IS specimens of 0. 

 viaculosa in the M. C. Z. collection. Critical study of this material 

 shows that half of it is in reality 0. savignyi, and I have even inclined 

 to the view that the two species are identical. But in the other half 



