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. From 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 
Fic. 6% —Thecopsammia socialis, PouRTALES. Once anda half the natural size. (No. 57, 1869 
by the dredge, but they fall an easy prey to the 
‘hempen tangles.’ 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 
