172 



THE VOYAGE OF H.M.S. CHALLENGER. 



sible to say from what depth the fishes came. In the shallower dredgings, from 2175 to 

 1000 fathoms, on the edge of the Azores plateau, a larger number of species and individuals 

 were found than in the deeper water, nearly all groups being represented. 



Tlie Ophiuroidea. — The Challenger collection of Ophiurans has been carefully 

 examined and described by Mr. Theodore Lyman, who furnishes the following rdsume 

 of his Keport : l — " In no group, perhaps, was our knowledge more extended by the 

 explorations of the Challenger than in that of the Ophiuroidea. The number of known 

 living species was increased from 380 to about 550, or nearly by one half, while the corre- 

 sponding increase of novel groups is indicated by the addition of twenty genera. By far the 



Fig. 71,— Ophionwsium pulcheUnm, Wyv. Thorns. 0ml aspect of the disk; seven times the natural size. 



greater number of new species are of the deep-sea fauna ; that is to say, they occur below the 

 100 fathom line, so that this Expedition has furnished the first opportunity of comparing 

 the littoral and the deep faunae over a wide extent of the oceans of the world. The result 

 is that these Echinoderms are found to be animals which live very much in defiance of tem- 

 perature, light, and water pressure. Something other than environment has determined 

 their growth ; or rather, their growth is not affected by an important part of their 

 environment. To be sure there are some genera which are confined to the profound 

 region of cold, darkness, and crushing weight; such are Ophiotrochus, Ophioplinthus, and 

 Ophiernus; but there are others, for example Amphixvra and Ophiacantha, which arc 



1 Zool. Chall. Exp., part xiv., 1882, 



