CHAP. IX.] 



THE DEEP-SEA FAUNA. 



433 



I have already adverted to the danger we run in. 

 estimating the relative proportions in which any 

 special groups may enter into the sum of the abyssal 

 fauna, by the proportion in which they are recovered 

 by any single method of capture. Prom their con 

 siderable size, the length and rigidity of their strag 

 gling rays, and their habit of clinging to fixed ob 

 jects, the Echinodermata are not very readily taken 



FIG. 69. Thecopsammia socialis, POUETALES. Once and a half the natural size. (No. 57 1869.) 



by the dredge, but they fall an easy prey to the 

 'hempen tangles. 5 It is possible that this circum 

 stance may to a certain extent exaggerate their 

 apparent abundance at great depths, but we have 

 direct evidence in the actual numbers which are 

 brought up, that in some places they must be won- 



F F 



