MUSEUM OF COMPARATIVE ZOOLOGY. 0O8 



As this number of the Bulletin was going to press I received from Dr. 

 Liitken his Addit amenta ad Historiam Ophiuridarum, Part III, 18G9, 

 in which he enters into a critical discussion of the relations of the gen- 

 era of Ophiurans. The work is done with that ability and thoroughness 

 which usually characterize the Scandinavian naturalists above all others 

 of Europe. This is not, however, the place to give a review of the 

 paper, and I shall merely notice a few points that particularly concern 

 the Caribbean fauna. 



Two interesting genera are added to those known, from the West 

 Indies, — Ophionema, which stands in the Amphiura group next to 

 Ophiopeltis, from which it differs by having no disk scales at all, and by 

 having all the arm-spines of the same form; and Ophionephthi/s, which 

 is in the same group, and characterized by a disk covered partly by 

 naked skin, while there is a frame of scales round each pair of radial 

 shields, and a line of them along the cdge-of the disk. The species are 

 Ophionema intricata and Ophionephthys UmicoJa. There is also an 

 Ophiacantha {0. pentacrinus) which, as the description will show, is 

 very near to, if not identical with, my 0. mcridionalis. In treating of 

 Opkiactis clavigera Ljn., Dr. Liitken has run against the precise 

 difficulty I have (see Ophiactis humilis) ; and the anomalous posi- 

 tion of the species is shown by the fact that, while he places it with 

 Ophiacantha, I incline to retain it with Ophiactis. The real trouble is, 

 that so many new forms are constantly discovered, that the limits of the 

 old genera are as constantly found to be defective, particularly when 

 those limits are established on characteristics more or less partial. For 

 example, take Dr. Liitken's description of Ophiactis: " Squarruc disci 

 spinulis brevibus plus minus obsitae. Brachia 5 - G satis brevia. Spina? 

 laterales 5-7, papilla ambulacris 1, orales 1 -2." Now, then, what is to 

 be done with 0. plana, that has no disk spines ? Or what should we do 

 with a species that had two tentacle scales, or four arm-spines? Or 

 what is the meaning of " satis brevia," as applied to the arms? I am 

 free to acknowledge that my own genera Ophiophragmus and Ophiocni- 

 da, among the Amphiura, could be catechized in like manner ; but I do 

 not see that Amphipholis Ljn. is a better substitute.* In fact, Dr. 

 Liitken, with his usual modest judgment, alludes to the transition state 

 of his classification when he says: "Je ne doute nullement aussi que 



* See rem::;ks on the genus Amphiura, p. 335. 



