282 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



gymna which Ljungman created in 1866 and of which the type is (9. 

 elegans from Singapore and Hongkong. This genus must, therefore, 

 disappear from zoological nomenclature. The species which I de- 

 scribed in 1905 under the name of Ophiocampsis inermis is synony- 

 mous with Ophiogymna elegans, and Duncan's Ophiocampsis pelli- 

 cula must be called Ophiogymna pellicula. We shall see later on that 

 the genus Ophiogymna, the characters of which I shall define, must 

 include, in addition to these two species assigned heretofore to the 

 genus Ophiocampsis, a few others previously placed by myself in the 

 genus Ophiothrix. Before beginning the discussion of the characters 

 and the limits of the genus Ophiogymna, I shall give some notes on 

 the specimens collected by the Albatross. 



These specimens agree very well with those collected by the Siboga 

 in the Sunda Archipelago which I described under the name of 

 Ophiocampsis inermis. All these individuals are distinguished from 

 O. pellicula by the entire absence of spines or of granules from the 

 disk. The diameter of the disk varies between 5 mm. and 9 mm.; 

 two specimens from station 5151 are extremely small; I shall speak 

 of them further on. 



The general coloration of the specimens in alcohol is pinkish, tend- 

 ing more or less toward yellow, with more or less numerous red dots 

 on the dorsal surface of the disk ; there is usually a spot outside of 

 each radial shield and another within the two shields of each pair. 

 The arms ordinarily show annulations formed by an assemblage of 

 small red dots. 



The dorsal surface of the disk is provided with a rather thick and 

 folded integument including some calcareous nodules, but it is quite 

 without granules or spines. The radial shields are in part covered 

 by the integument and the region which remained naked, oval in 

 shape, is more or less extensive, as may be seen by comparing the two 

 photographs which I give (pi. 43, figs. 4, 5). The ventral surface of 

 the disk in the interradial spaces is covered with an integument iden- 

 tical with that of the dorsal surface, but thicker and with more de- 

 veloped calcareous nodules, though without the least trace of spines 

 or of granules. 



Contrary to general opinion, the upper arm plates, instead of being 

 absent, are assuredly present ; to be sure they are hidden under a more 

 or less thick integument, and in alcoholic specimens they are invisi- 

 ble ; but in order to find them it is only necessary to examine dried 

 examples (figs. 5, 6). These plates are broken up into numerous un- 

 equal and irregular fragments, especially in the proximal region of 

 the arms where it is not ordinarily possible to distinguish among 

 these fragments the borders of the successive segments. But these 

 borders usually appear at some distance from the disk. In 0. pelli- 



