10 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the mouth parts, are in reality of great significance. Moreover, it 

 must be recognized that the species assigned by Matsumoto to his 

 genus Amphiactis have external characters which in no way accord 

 with those of the genera Amphiura (taken in the broad sense) and 

 Ophiactis, between which they were distributed. 



In mentioning the several genera which he places in the subfamily 

 Amphiurinae Matsumoto notes "Amphiura, including Ophioneph- 

 thys,^ and also " Ophiocentrus, including Amphiocnida^ He be- 

 lieves, therefore, that the species of the genus Ophionephthys should 

 be placed in the genus Amphiura, and those of the genus Amphi- 

 ocnida in the genus Ophiocentrus. 



H. L. Clark has not adopted this point of view, maintaining as 

 distinct the genera Amphiocnida ('15, p. 236) and Ophionephthys 

 (p. 239). I shall have occasion to revert to this subject when I dis- 

 cuss Amphiura vadicola and Ophiocentrus aculeatus. 



4. Chilophiukida. — The observations which I have to offer con- 

 cern the families Ophiolepididae and Ophiodermatidae, more par- 

 ticularly the old genera Ophiura and Ophioconis. 



Not only am I adopting the divisions established by Matsumoto, 

 but from now on I shall use the name Ophiura in place of Ophio- 

 glypha, which I have always used heretofore in order to be in agree- 

 ment with the nomenclature which echinologists are now using and 

 which H. L. Clark has adopted in his " Catalogue." I should state, 

 however, that in using the name Ophioglypha as I did I had hoped 

 primarily to avoid misconceptions. It is agreed that the rule of 

 priority requires the use of the name Ophiura, but everyone knows 

 that sometimes exceptions must be made to the strict application of 

 the rule if it is not to lead to impossible or even ridiculous results 

 (see the remarks published by Mortensen in 1910 and 1911 regarding 

 the strict application of the rule of priority to the echinoderms). 



I have always believed, and still do, that it would be better to 

 set aside the rule of priority than to introduce fundamental changes 

 in the nomenclature. The substitution of the name Ophiura for 

 Ophioglypha would for a time create confusion, as many authors, 

 Lyman for example, have used Ophiura as a synonym of Ophio- 

 derma, Such use runs back for a very considerable time, and since 

 1882 Ophiura, when it has been used, has appeared more commonly 

 as a synonym of Ophioglypha than as a synonym of Ophioderma. 

 The chances of confusion thus have been becoming more and more 

 remote, and that is why I shall henceforth conform to the prefer- 

 ences of my colleagues. 



It was in 1915 that Matsumoto first established in the old genus 

 Ophiura (taken in the broad sense) a certain number of divisions 

 representing separate genera, as follows : 



