OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 211 



difference has to do with the size of the subjects. In the type of the 

 species, which is a little larger than the Albatross specimen, the rela- 

 tive width of the under arm plates is far from being as pronounced 

 as in the specimen from Trincomalee, in which the disk reaches 17 

 mm. in diameter; in the last, the ventral plates are very much 

 broader than long, and their distal border is no longer convex ; it be- 

 comes sometimes even slightly concave. I do not believe that this 

 slight difference in the form of the under arm plates necessitates a 

 specific separation, and I believe that the name O. aspidota may be 

 perfectly well applied to the Albatross specimen. 



However, it must be noticed that this individual differs in its 

 coloration from my specimen from Trincomalee. Must it be assumed 

 from this that the latter is not an O. aspidota? I do not think so, 

 and we know other species of OphiotJirix in which the blue coloration 

 replaces the red coloration, or the reverse; I have been able to ob- 

 serve, for example, that in 0, proquinqua the general coloration is 

 sometimes blue and sometimes red. 



I may add that the club spines of the dorsal surface of the disk 

 and the arm spines show the same microscopical characters in the 

 specimen from the Philippines and in mine from Trincomalee. 



Miiller and Troschel's original specimen is given as coming from 

 the East Indies; Lyman mentions O. aspidota from Celebes; the 

 species is also known from Madagascar, from Ceylon, and from 

 Kurrachee. 



OPHIOTHRIX BELLAX, new species. 



Plate 47, figs. 1-3; plate 97, fig. 4. 



Locality. Unknown. 



One specimen (Cat. No. 41026, U.S.N.M.). 



Description. The diameter of the disk is 9 mm. The arms must 

 be rather long, though none is complete; one of them is preserved 

 for a length of TO mm. and it only seems to lack a small part of its 

 distal portion. 



The disk is rounded. The dorsal surface is uniformly covered 

 between the radial shields with rather stout, elongated, somewhat 

 unequal, and irregular spines, showing at different heights some 

 rather strong conical and pointed teeth, their tips ending in two 

 or three short and pointed spinules (pi. 97, fig. 4a) . In the midst 

 of these spines are some cylindrical club spines terminated by 

 two or three unequal spinules, and all intermediate forms between 

 the longest spines and the shortest club spines may be found; but 

 the spines are in the majority; this whole investment is rather 

 close. At the periphery of the disk the spines become progressively 

 shorter, and only the club spines pass over onto the ventral sur- 

 face. The radial shields are covered, but they only bear small club 



