284 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Genus OPHIOGYMNA. 



I may recall that Ljungman in creating the genus Ophiogymna 

 characterized it by the presence of a thick integument covering the 

 whole dorsal surface of the disk and leaving exposed only the distal 

 extremities of the radial shields; this integument includes within it 

 calcareous nodules with poorly defined outlines. The mouthpieces 

 are formed as in the genus Ophiothrix. The arms are very long, 

 and the arm spines, numbering from five to ten, are often three times 

 as long as the segment ; they are more or less glassy and denticulated. 

 Ljungman does not make any mention of the characters of the upper 

 arm plates, either in his short diagnosis of the genus or in the very 

 short description which he gives of 0. elegans. 



Liitken in 1869 ('69, p. 60) added a few notes to Ljungman's de- 

 scription, and he says especially on the subject of the upper arm 

 plates " egentlige Armrygplader synes at mangle i dets. . . ." 



In 1886 Duncan created the genus Ophiocampsis, which is a true 

 synonym of the genus OpMogymna. He characterized his new 

 genus by the presence of an integument covering the disk as well as 

 the radial shields and bearing a few spinulous club spines; he for- 

 mally stated that the upper arm plates are lacking, but that an in- 

 tegument including small calcareous plates covers the dorsal surface 

 of the arms, which is broad and convex, etc. 



The two genera Ophiogymna and Ophiocampsis have always been 

 listed separately in the family Ophiotrichidae by all authors since 

 1886, and Matsumoto also mentioned both of them in 1915. H. L. 

 Clark was the first to recognize the identity of the two, and in his 

 recent catalogue of the living ophiurans he gives OpKwcqmpsfe 

 inermis as a synonym of Ophiogymna elegans he places in the same 

 geus, Ophiogymna, O. pellicula Duncan. The genus Ophiocampsis 

 thus falls into synonymy and must disappear. 



Judging from the supplementary remarks given by Liitken on the 

 subject of Ophiogymna elegans ('69, p. 60), and also from the 

 diagnosis of the genus Ophiocampsis given by Duncan, the upper 

 arm plates should be completely lacking. But we have seen that 

 this statement is quite inexact and that upper arm plates occur; it 

 is true, however, that they are concealed by the integument and more 

 or less broken up in the adult animal. It is therefore necessary to 

 rectify the diagnosis of the genus Ophiogymna, taking into considera- 

 tion the presence of these plates ; and I emphasize this point, for the 

 same error is found repeated in different works; for example, De- 

 lage, 10 Mclntosh ('11, p. 161), and Meissner 11 all say that the upper 



10 Traits de zoologie concr&te, vol. 3, p. 156. 



11 Bronn's Thierreich, vol. 2, Abtb. 3 ; Echinodermen III, Schlangenseesterne, p. 942. 



