32 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
Remarks.—None of these specimens exceed a size of 140 mm. in 
diameter. This is also the case with the several specimens that I 
have myself collected in the Philippine Sea and at the Kei Islands. 
In Dr. H. L. Clark’s Catalogue of the Recent Sea-Urchins in the 
British Museum the Challenger specimens are stated to range from 
26 to 120 mm. in diameter. Déderlein’s and de Meijere’s largest 
specimens were, respectively, 115 and 130 mm. in diameter. It may 
then rather safely be said that Agassiz’s statement that this species 
reaches a size of 200 mm. in diameter must be a mistake—probably 
a misprint for 120 mm. 
The specimens at hand, some of which are in good and others in 
poor condition, are in general quite typical examples of this species, 
although in the specimens from stations 5241, 5242, 5243, and 5245 
the spines of the aboral side are more slender and the tubercles cor- 
respondingly smaller, which makes them look somewhat different 
trom the typical coarse-spined form. I do not, however, find any other 
characters distinguishing these specimens from the typical form, so 
that I must regard them as belonging to this same species, possibly 
representing a local race, though scarcely characteristic enough to be 
distinguished as a separate variety. 
The specimens from station 5415 are red-brown, the others more 
dark purple, or nearly black—if not faded, as is the case with the 
specimens from station 5625. As they do not differ in any other 
way from the darker specimens, they must likewise be regarded as 
true M. tuberculata. 
One of the specimens from station 5415 and some of those from 
station 5516 are interesting in carrying on their oral side examples 
of the epizoic ophiuran Ophiosphaera, all of them with the oral side 
turned away from the sea-urchin. Evidently this is a new species, 
but like O. insignis it carries the male on the oral side, covering the 
mouth of the female specimen and the arms of the female alternating 
with those of the male. 
As was found to be the case with several species among the 
echinothurids, Micropyga tuberculata feeds largely on plant re- 
mains, from both phanerogams and algae, that have sunk to the 
bottom of the sea. But other bottom material also may form part 
of its diet. 
MICROPYGA VIOLACEA de Meijere 
Micropyga violacea pe MEtJERE, Siboga Echinoidea, p. 63, pl. 4, figs. 29, 30; 
pl. 15, figs. 282-234, 1904. 
Localities Station 5114; Verde Island passage; Sombrero Island 
bearing N. 36° E., 7.2 miles distant (lat. 13°36’11’’ N., long. 
