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Show 1884.] SPECIES O F OREASTER. 71 cellariae, for they not only cover the reticulating bars of the dorsal ossicles, but invade also the poriferous areas; the granules, of ordinary character, are confined to the knobs and spines, the tips of which, however, they do not cover. Along the lophial line the projections are always rather tubercular than spinous, but the five spines at the angle of the apex and the central spine within are exceedingly well developed and rather acutely pointed. A few rounded tubercles, similar in character to those of the lophial line, are developed at the sides of the disk. In dried specimens the disk rises up in an altogether turriform fashion. Madreporite small, rather obscure, on one of the sides of the disk. Colour (dried) greyish sandy. Hab. Indian Ocean generally. Measurements :- R 165 130 118 100 r 62 44 46 37 Height of disk. 58 45 31 27 Length of longest spine .. 15 14 21* 18 It is to be observed that there are some not unimportant variations in the characters of the spines : those of the lophial line are sometimes sharp, are not always blunt; the apical spines appear to be liable to early division into two or three secondary apices, or they may give off a spur or projection, and, lastly, the processes at the sides of the disk may become quite sharp. OREASTER HIULCUS. Oreaster hiulcus, M . Tr. Syst. Ast. p. 48. The most important difference between this species and the preceding would appear to be the character of the granulation of the dorsal ossicles and the much feebler development of pedicellariae. Miiller and Troschel, who alone (Syst. Ast. p. 48) have given a satisfactory account of the species, give the habitat as the Indian Ocean ; Prof. Perrier would appear to know of it only as from Zanzibar and Mauritius. OREASTER HEDEMANNI, Liitken. O. hedemanni, Liitken, Vidensk. Med. 1871, p. 263. " Dorsum sat altum, brachia triangularia, mediocria, acuta ; radius stella? major minorem duplum et dimidium aquat; tesselce mar-qinales utrinque c. 15, dorsales ventralibus magnitudinc cequales, parte externa brachiorum forsan excepta hand alternantes et in peripheria stella? formanda cequaliter participes; non nut Ice (dorsales sc. 5, ventrales 5-6, ad angulos stella? sites, nee non 1 vel versus apices brachiorum locum tenentes) tubercula minuta gerunt; area? porifera? regulares, sejunctce, poris numero mediocri, juxta tesselas marginales maxima?; tubercula dorsualia quinque sat magna apice nuda, spatiis diametros basales a?quantibus inter se separata, tuberculum centrale mediocri circumdant; series fere |
