182 BULLETIN" 100, UNITED STATES NATIONAL MUSEUM. 



Amphioplus relictus can not, therefore, be placed in the genus 

 OpMophragmus, and the arrangement of its mouth papillae necessi- 

 tates placing it in the genus Amphioplus. 



This question was interesting not only because of the necessity of 

 making a correct generic determination, but also because there de- 

 pends upon the answer a case of synonymy, for the ophiuran from 

 the Mergui Archipelago which Duncan described under the name of 

 OpMophragmus affinis shows sigular external resemblances to our 

 species, as may be seen in glancing over the figures published by Dun- 

 can ('86, pi. 8, figs. 4 and 5) ; these resemblances are even sufficiently 

 marked so that one is justified in asking whether it does not deal with 

 the same species. We notice, however, that the mouth shields of 

 O. affinis have a form different from that which we know in 

 A. relictus, and I have never observed in this latter a form identical 

 with that which Duncan has figured. But the characters furnished 

 by the study of the internal skeleton prevent all possibility of bring- 

 ing them together. 



Duncan had noticed the mixed characters of his species, and he con- 

 fessed the difficulty that he had in placing it either in the genus 

 OpMophragmus or in the genus Amphiura (that is, in the present 

 terminology, in the genus Amphioplus). I believe that it would be 

 more correct to place the species from the Mergui Archipelago in the 

 genus Amphioplus, but this question has no place here. What is of 

 consequence to decide is whether OpMophragmus affinis Duncan is or 

 is not a synonym of Amphioplus relictus (Kcehler). If Duncan's 

 figures and description are correct in regard to the characters of the 

 genital plates, there can be no question of considering these two 

 forms as synonjTns. Until proof to the contrary is shown, I have 

 therefore believed it necessary to maintain Amphioplus relictus as a 

 species distinct from OpMophragmus affinis. 



Even if it were proved that Duncan's OpMophragmus affinis was 

 not an OpMophragmus, but an AmpMoplus, and that my Amphio- 

 plus relictus was identical with it, our species would not bear any 

 other name than that of Amphioplus relictus. In that case Duncan's 

 species would according to rule assume the name of Amphioplus 

 affinis. But the name affinis has been applied to an ophiuran from 

 south Georgia described by Studer in 1885, while Duncan's species 

 dates from 1886. It is for the Antarctic species that the name Am- 

 phioplus affinis must be reserved. If Duncan's species must be placed 

 in the genus AmpMoplus, it will be necessary to give it another spe- 

 cific name; the simplest solution would be to give it the name of O. 

 relictus. This is, moreover, the nomenclature which H. L. Clark 

 adopted in 1915. He considers Amphioplus relictus (Kcehler) as a 

 synonym of OpMophragmus affinis Duncan, and in his catalogue 

 ('15, p. 697) he cites A. relictus under No. 697, while in the table 



