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

142 COLLECTIONS FROM MELANESIA.become less conspicuous and much reduced ; the white lines alongthe arm are broken into by blue patches, much less extensively developedthan in the dark form ; on the lower surface of the armthe blue lines may be present as continuous" tracts, or they may hereand there be interrupted by white.Port Curtis ; Thursday Island ; Port Darwin.16. Ophiothrix striolata.Lyman, p. 36.Thursday Island.17. Ophiothrix galatesB.Lyman, p. 36.Port Darwin.18. Ophiothrix ciliaris.Lyman, p. 85.Port Jackson, 0-5 fms. ;Port MoUe.„ 19. Ophiothrix rotata.Martens, Arch.f. Nat. 1870, p. 258.A single specimen, without doubt referred to this species, differsin one or two points from tbat described by Dr. von Martens. Inthe Berlin-Museum specimen the diameter of the disk is 7 millim.,and the length of the arras 35 millim. In our specimen the armsmust have been nearly 150 millim. long, while the diameter of thedisk is 12 millim. The upper spines are not more than twice thewidth of the arm, instead of four times. The original describermakes two statements with regard to the colour of the oral shields :— " Unterseite der Bcheibe mit den Muudschildern und die Armstachelnblass " ; and " Das der Madreporenplatte zi;gehorige Mundschildist merklich grosser, an den Heiten nicht eingebuchtet undweiss, nicht wie die andern violett." In the specimen now underexamination there is some violet marking on each one of the mouthshields.Thursday Island, 3-4 fms.So far as the present collection allows me to form any ideas withregard to the range of variation within the limits of a " species," andthe value of the colour-markings on which previous investigators havevery much greater than waslaid, and, as it seemed, justifiably, very considerable stress, I am inclinedto the view that the variation issupposed, and that, after all, colour-marking, though an importantaid in the discrimination of the species, can hardly be said to havethe value which has been attached to it. The doubts first raisedby a study of 0. martensi (vide supra) are not a little strengthenedby the three specimens now lying before me, which, I have little