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Show 1884.] SPECIES O F O R E A S T E R . 73 to the tips of the spines. Madreporic plate rather small, not conspicuous. Colour (when dry)-lower surface reddish, upper reddish where the granules are developed, with grey poriferous areas ; in some cases the dried specimens are almost white, but this may be due to the mode of drying. The above description has been drawn up from a set of five specimens, which were collected at the same time and place (between tide-marks, at the Mozambique, in M a y 1882) by Dr. Coppinger, H.M.S. 'Alert', and illustrate the exactness of the statement of Dr. von Martens :-" Aile diese Variationen kreuzen sich so sehr durchein-ander, dass man darnach keine irgendwie bestimmbaren Lokalvarie-taten aufstellen kann"1. The variations are so marked that it seems to be impossible to follow Dr. von Martens in establishing definite " varieties." The exact state of the case is, I think, this. The strength of the marginal and ventral plates, with their coarse granulation, is sufficient for the safety of the Starfish ; the spines are additional defences that are not constantly needed, and are developed more according to the conditions of individual environment than in obedience to the necessities of the species. They are organs which have begun to disappear, and their importance to their possessor may be judged of by the extent to which they vary in number and size on the different arms of one and the same individual. The species stands midway between 0. alveolatus, in which inferomarginal spines are also developed, and O. nodosus, in which there are no marginal spines at all. Hab. Indian Ocean (Mauritius, Timor). R 110 95 80 64 r 40 34 28 26 Greatest breadth of arm .... 35 34 31 26 OREASTER ALVEOLATUS. Pentaceros alveolatus, Perrier, Rev. Stell. p. 243. At first sight this species has the most remarkable resemblance to O. lincki, but it is at once to be distinguished from it by the constant possession of inferomarginal spines. R=2*7r. Disk very high, lophial line well marked; lophial spines well developed ; apical very prominent. The arms diminish but little in breadth from the proximal to the distal end. About 21 marginal plates ; at the angles the inferomargiuals form the sides, while the superomarginals are rather obscure, and these inferomarginals are provided with rather short spines ; the superomarginals gradually become larger, and oust the inferior plates from any share in forming the sides of the arms, while they develop prominent spines ; towards the tip of the arm spines, or spinous tubercles, reappear on the inferomarginal plates. Adambulacral spinulation diplacanthid; five or six spines in the inner row, not remarkably delicate ; those of the outer row pretty stout and arranged by twos or threes. A spiniform pedicellaria is 1 Arch, fiir Naturg. xxxii. 1866, p. 79. |