Report on the zoological collections made in the Indo-Pacific Ocean ...

KCHlNODERMATAj 141broader than long. Six arm-spines, the uppermost the longest, aslong as two or three arm-plates, swollen at their tip, only faintlythorny. One tentacle-scale.Disk with a large number of blue patches and dots ; arm-platesabove faint reddish pink, with dots of blue at the sides, and broadtransverse bands of blue at regular intervals. Colour-markihgsbelow less pronounced.Port Jackson, 0-5 fms.Lyman^ Chall, Rep. p. 218.14. OpMothrix caBspitosa.Though the Challenger ' ' found but few representatives of thisspecies, it is apparently one of the most common in the neighbourhoodof Sydney.Port Jackson, March 1881.Lyman, p. 36.15. OpMothrix martensi.If I am right in ascribing to this species examples from ThursdayIsland and Port Darwin, it is one which must be regarded as exhi-*biting very remarkable variations in coloration. The original specimens,collected by Prof. Semper in the Philippines, were describedby Mr. Lyman as being in colour, " above, bright indigo, with adarker line along the arm, bounded by a lighter one on either side ;below, paler indigo, with a white line along the arm." In a smallerspecimen, " the blue lines along the arms were continued to thecentre of the disk, but were not margined by lighter liucs." In thetwo specimens collected on "Aug. 7, 1874" (in the neighbourhoodof the Fiji Islands), by the ' Challenger,' and determined by Mr.Lyman, I observe that there is a faint indication of a white line oneither side of the blue lines on the disk, and that the white lineon the ventral surface is, at places, broken across by a patch ofindigo.On either side of these " typical specimens " there would appearto be a light and a dark variety. In the latter the whole creaturemay be deep purple, the two white lines on the arms being at regulardistances invaded by purple patches of such a size as to leave onlyspaces of white equal to themselves ; and as these patches are symmetricalon either side of the middle line, the original white linescome to be represented by nothing more than paired patches of white ;similarly the white line below disappears, or rather is forced out tothe sides, and appears only as a thin marginal line. The lightvariety is no less interesting ; with the exception of the radiatinglines, the disk above is altogether white, and even these lines may