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Show 296 MR. F. P. BEDFORD ON MALAYAN ECHINODERMS. [Mar. 20, Oreaster nodulosus, F. J. Bell, Proc. Zool. Soc 1884, p. 66. Reference, v. Martens, Archiv fiir Naturg. 1866, p. 77. Locality. This species is found not uncommonly in about a fathom of water on the shore of the lagoon off the east side of Singapore Island. Distribution. Indian Ocean, Eastern Archipelago, and N. Australia. The systematic classification of the genus Pentaceros offers similar difficulties to those found in the Echinoid Diaclema ; in both cases we have exceedingly variable groups of individuals in which the norm of the variations is different in different localities. The four " species " Pentaceros turritus M . & T., P. hiulcus M . & T., P. muricatus Gray, and P. alveolatus Perrier, which Professor Bell describes as " apparently distinct," are based on characters which are admittedly subject to very great variation ; and while Prof. Bell instances the presence or absence of marginal spines as a character by which " we can always safely discriminate between 0. lincki (=P. muricatus) and 0. nodosus ( = P. turritus)" (loc. cit. p. 59), at the same time Dr. Martens had named two varieties of P. muricatus (var. mutica and var. intermedia) in which the marginal spines completely fail: this of course is entirely due to the fact that no two observers are agreed as to the best set of characters to select for specific diagnoses, and in consequence a totally different grouping of the same series of specimens would be resorted to by different systematists. Whether it is advisable in such a case to unite all the forms under one specific name, as has been suggested for the Pacific Diademas by Prof. Loven, I do not feel in the least competent to express an opinion. Specimens both with and without a central apical tubercle occur at Singapore as elsewhere, and in the former case the apical tubercles may be much longer and sharper than in the latter, in which they are usually mamilliform ; I do not know if individuals with the marginal spines developed occur in the locality. Two specimens gave the following measurements :- R (act. side) = 116 mm., r = 4 6 ; arm-breadth = 54 ; no. of marg. plates = 23 ; 9 lophial tubercles, 3 or 4 interradials. R (act. side) = 128 mm., ?- = 52 ; arm-breadth = 5S ; no. of marg. plates=27; 7 or 8 lophial tubercles, 4 interradials. 13. CULCITA NOVJE-GUINEiE, var. ARENOSA. Culcita novce-guinece, Muller & Troschel, Syst. d. Ast. 1842, p. 38. Culcita arenosa, J. O. E. Perrier, Revision des Stellerides, 1875, p. 264. References. C. Ph. Sluiter, Natuurk. Tijd. v. Ned. Ind. xlviii. 1889, p. 305 (C. schmideliana). CI. Hartlaub, Notes from the Leyden Museum, xiv. 1892, p. 65. R. Koehler, M e m. Soc. Zool. France, viii. 1895, p. 388. L. Doederlein, Semon's Zool. Forsch. in Austr. &c. Bd. v. Lf. 3, 1896. |