ECHINODERMS OF CHALLENGER BANK, BERMUDA. 361 



yet known from there is a very young one (disk about 3.5 mm. across) 

 taken by the 1903 expedition. The contrast in appearance between 

 this specimen and the young pumila just listed is very striking and 

 one finds it hard to consider them congeneric. For in pumila the 

 arms are rather short and stout with short, basally thickened arm- 

 spines and the disk has its scales pretty completely concealed under 

 the covering of elongated granules; whereas in riisei, the arms are 

 long and slender, with long, slender arm-spines, and the disk carries 

 no granules but is covered by a well-marked coat of scales. In both 

 cases, however, one is strongly reminded of the Ophiacanthidae and 

 it is only from the presence of evident dental papillae, and the char- 

 acter of the tentacle-scale, that the relationship, to the Ophiocomidae 

 can be deduced. 



ECHINOIDEA: SEA-URCHINS. 



Stylocidaris affinis. 



Cidaris affinis Philippi, 1845. Arch. Naturg., Jhg. 11, 1, p. 351. 

 Stylocidaris affinis Mortensen, 1909. Ech. Deutsch. Stidpolar-Exp., p. 52. 



The occurrence of this cidarid at Challenger Bank is of great 

 interest as it extends the known range of the species very considerably 

 to the northeast, so far at least as the western side of the Atlantic 

 is concerned. As affinis occurs in the Mediterranean, and probably 

 at the Cape Verde Islands, its occurrence near Bermuda helps to 

 bridge the gap between the West Indian and European areas. The 

 specimen taken by the party in 1903 is only 10 mm. in diameter and 

 has the primary spines only about 15 mm. long, but its identity seems 

 to be beyond cpestion. 



Centrechinus antillarum. 



Cidaris {Diadema) antillarum Philippi, 1845. Arch. Naturg., Jhg. 11, 1, p. 355. 

 Centrechi?ius antillarum H. L. Clark, 1918. Bull. Lab. Nat. Hist. Iowa, 7, no. 5, 

 p. 24. 



Two very young individuals were taken in 1903. They are about 

 8 mm. in diameter with primary spines about 16 mm. long. The 

 general color is quite different in the two, one having the primaries 

 light claret red, rather indistinctly banded with whitish, while the 

 other has them whitish distinctly banded with pale brown. 



