OPHIUROIDEA OF THE BAHAMA EXPEDITION. 3 



known that our northern butter-fish, when young, lives with 

 impunity beneath the disk and among the tentacles of the 

 great red jelly-fish (Cyanea arctica), which is deadly to other 

 fishes. 



It is probable, therefore, that in tropical waters many fishes 

 have acquired comparative immunity against the poisonous 

 stinging organs (cnidcs) of coral animals. If so, the utility of 

 the additional protection afforded by the imitative forms and 

 colors of so many of the coral-inhabiting ophuiroids would be 

 obvious. 



Professor Nutting has already described the colors of some 

 of these curious forms in his Narrative of the Expedition. 



In this report I have followed, in general, the order of se- 

 quence adopted by Lyman, but in the case of the Enryalce 

 and in the families Am^phiuridce, Ofthiacanthidce, and some 

 others, I have thought it desirable to alter his classification 

 considerably. 



I have also introduced the names and in some cases the 

 characters of the family groups, and have changed the limits 

 of several of them. Many of these were proposed bv Liitken 1 

 and by Ljungman 3 many years ago. 



Several new families are also now characterized. 



In describing the genera and species, I have generally used, 

 as a matter of convenience, the same terms, for the organs 

 and parts, that were used by Mr. Lyman in his various works 

 on this group, but have made a few obvious changes. I have 

 preferred to use oral shield instead of "mouth-shield", and 

 adoral shield instead of "side-mouth-shield". In the genera 

 allied to Amphiura, I have usually called the "outer mouth- 

 papillae" or papillae of the second oral tentacle, the distal oral 

 tentacle-scales to indicate their homology with the ordinarv 



'Addit. ad Hist. Ophiur., Part III; Synop. gen. Ophiur. ver., p. 87, 

 1869. 



2 Ophiuroidea viv. hucusque cognita enumerat, Ofvers. Kgl. Veten- 

 skaps-Akad. Forhandlingar, for 1866, 1867. 



