Bell — Echinoderms collected by the 8S. " Fingal." 527 



have been difficult, perhaps impossible, to have escaped from the 

 error of believing that more than one species of the genus had 

 been taken. The specimens differ so much from one another that 

 it is quite easy to find two which might be made " types " of 

 distinct species. The differences in structure are apparent to a 

 careful collector and during life, for I see by two pictures with 

 which Mr. E. W. L. Holt has been so obliging as to favour me, 

 that in life one is coloured above a bright-red, five patches of 

 which are deeper than the rest, while the other is greyish, with 

 five reddish-brown patches of varying degrees of intensity ; the 

 former the collectors describe as having small plates and small 

 spine-bases ; the latter as having " large plates or large spine- 

 bases." 



It will be remembered that Sir Wyville Thomson described 

 two species of " Calveria " from the " Porcupine " dredgiugs, and, 

 from the description that he gives of the colouration it might be 

 thought that Mr. Grreen got the same two forms, for of one Thomp- 

 son writes : ^ " The colour of the perisom is a brilliant deep rose, 

 inclining to claret-colour ; twenty bands of deeper shade run in 

 pairs, alternately closer, and more remote from one another, along 

 the ambulacral and interambulacral spaces. The ends of the 

 spines are pale pink, and the tube feet are nearly white." 



Of the second species he remarks:^ "The colour of the test 

 generally is greyish, but ten bands of purplish brown radiate 

 from the apical pole, shading oH into the grey of the test, and 

 giving a rich effect of colour to the upper surface. The spines 

 are whitish, and the ambulacral part grey tinged with purple." 



The colouration of tests, however, does not often go far in 

 helping in the discrimination of species of Echinoids ; and in the 

 large series (preserved, indeed, in spirit) which has passed through 

 my hands, I have found a considerable degree of variation in the 

 extent and intensity of the bands or patches of colour ; and this 

 may go so far that some specimens are quite pale. When such a 

 specimen is set side by side with one that is a brilliant pink all 

 over, it is of course impossible to believe that they are examples of 

 one and the same species. 



Another point in which there is great variation is the extent of 



1 Phil. Trans, 169 (1874), p. 740. « Zoc. cit., p. 743. 



