2 NATURAL HISTORY BULLETIN. 



This collection is peculiar in lacking many common species 

 which were taken at numerous stations and in large numbers 

 by the '-Blake Expedition". Such species belong largely to 

 such genera as Ophioglypha, Ophiomusium. Amphiura, etc. 

 These live, for the most part, on muddy or sandy bottoms, or 

 buried just below the surface, and are only to be obtained by 

 the use of the dredge or trawl. But as the Bahama Expedi- 

 tion worked largely upon the hard bottoms and used the 

 tangles relatively much more than the dredge, the absence of 

 many of the common species is easily understood. 



On the other hand, and for the same reasons, the collection 

 is relatively rich in those species and genera that live on hard 

 bottoms and cling to the branches of gorgonian corals, hy- 

 droids, etc., by means of their long, coiled arms. 



Such species are best obtained by the tangles. Some of 

 these belong to the Ophiurce; such as Sigsbieaand Hemieurycile ; 

 but most of them belong to the Euryalte. Many of these are 

 simple armed species of the genera Ophiocreas. Astroschcema, 

 Astroporpa, Astronyx, Asti'ogomphus ; others are of the general 

 Astrophyton and GorgonocephaJus. in which the arms are 

 many times forked. 



Some of the long-spined genera, like Ophiacantha, Ophio- 

 mitra, Ophiothrix, etc.. also live among the branches of gor- 

 gonian corals, or clinging to other organisms, so that they are 

 easily captured by the tangles. Such genera are well repre- 

 sented in this collection. 



Most of those species with long, coied arms, adapted for 

 clinging to the branches of gorgonian corals, are remarkable 

 for imitating closely, in various ways, the forms and colors of 

 the corals on which they live. This must afford them a con- 

 siderable degree of protection against predacious fishes, in 

 addition to the direct protection due to the stinging powers of 

 the corals themselves, which is sufficient to cause most fishes 

 to avoid them. 



I have observed that some of the northern plectognath 

 fishes (file fishes) will feed upon hydroids. It is also well 



