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

ECHINODKRMATA. 143doubt, will be seen, when a large series is to hand, to be nothingmore than varieties of 0. rotata. As none of the arms are complete,the measurements I could give might only be deceptive ; in them theupper arm-spines are proportionately lai'ger than in the specimenalready spoken of; the bands separating the plates, the character ofwhich has given rise to the specific name, may vary -in breadth on oneand the same disk; and the granules may be in narrow or broad bands,and may be so greatly elongated that they may more correctly bespoken of as spines ; the marking would by some be spoken of asexceedingly characteristic, for there extend from the disk on to thearms two lines of dots of blue ; at every fourth plate, when regular,the two dots of either side fuse, and the spot enlarges into a bluepatch ; an exactly similar marking is to be seen on the lower surface.In the specimen unhesitatingly placed with 0. rotata there isnot this definite arrangement of the dots.I have thought it right to direct attention to these peculiarities,but a full and satisfactory discussion of the subject must be basedon a much larger series of specimens.These examples were also from Thursday Island.20. Ophiothrix punctolimbata.Martens, Arch.f. Nat. 1870, p. 257.Port Curtis ; Port Molle ; Thursday Island, 3-4 fms. ; Prince ofWales Channel ; Warrior E-eef.The specimen from Port Curtis, which is smaller than the others,has the lateral spines proportionately longer, more echinulated, andmuch more glossy.Lyman, p. 35.21. Ophiothrix longipeda.Port Curtis ;Port Molle.22. Ophiothrix microplax.Disk large, covered with short spines, less thick on the radialshields ; ends of the not-thorny arm-spines faintly clavate. Proportionof arms to disk about 6 to 1.The disk is rather large (20 millim. in diameter) and is coveredwith very short spines, which may almost be described as spinousgranules ; these are not so closely packed on the radial shields or onthe actinal surface as on the rest of the disk. The radial shieldsare small, elongated, triangular, the straight base of the one facesthat of the other ; the plates of each pair are separated by severalelongated scales, which carry a few longer spines. There is someimbrication of the scales on the actinal surface of the disk.