ECHlNODEEMAIAi 141 



broader tlian long. Six arm-spines, the uppermost the longest, as 

 long as two or three arm-plates, swollen at their tip, only faintly 

 thorny. One tentaole-soale. 



Disk with a large number of blue patches and dots ; arm-plates 

 above faint reddish pink, with dots of blue at the sides, and broad 

 transverse bands of blue at regular intervals. Colour-markihgs 

 below less pronounced. 



Port Jackson, 0-5 fms. 



14. OpMothrix csespitosa. 

 Lyman, Chdll. Rep. p. 218. 



Though the ' Challenger ' found but few representatives of this 

 species, it is apparently one of the most common in the neighbour- 

 hood of Sydney. 



Port Jackson, March 1881. 



15. OpMothrix marteusi. 

 Lyman, p. 36. 



If I am right in ascmbing to this species examples from Thursday 

 Island and Port Darwin, it is one which must be regarded as exhi- 

 biting very remarkable variations in coloration. The original spe- 

 cimens, collected by Prof. Semper in the Philippines, were described 

 by Mr. Lyman as being in colour, " above, bright indigo, with a 

 darker line along the arm, bounded by a lighter one on either side ; 

 below, paler indigo, with a white line along the arm." In a smaller 

 specimen, " the blue lines along the arms were continued to the 

 centre of the disk, but were not margined by lighter lines:" In the 

 two specimens collected on "Aug. 7, 1874" (in the neighbourhood 

 of the Piji Islands), by the ' Challenger,' and determined by Mr. 

 Lyman, I observe that there is a faint indication of a white line on 

 either side of the blue lines on the disk, and that the white line 

 on the ventral surface is, at places, broken across by a patch of 

 indigo. 



On either side of these " typical specimens " there would appear 

 to be a light and a dark variety. In the latter the wbole creature 

 may be deep purple, the two white lines on the arms being at regu- 

 lar distances invaded by purple patches of such a size as to leave only 

 spaces of white equal to themselves ; and as these patches are sym- 

 metrical on either side of the middle line, the original white lines 

 come to be represented by nothing more than paired patches of white ; 

 similarly the white line below disappears, or rather is forced out to 

 the sides, and appears only as a thin marginal line. The light 

 variety is no less interesting ; with the exception of the radiating 

 lines, the disk above is altogether white, and even these lines may 



