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Show 1900.] MR. F. P. BEDFORD ON MALAYAN ECHINODERMS. 285 11. LAGANUM, sp. ? (Plate XXIII. figs. 7 a, b.) Four small specimens were found among a number of individuals of Laganum depressum and decagonale which I cannot ascribe to either of these species. It seems possible that they may be hybrid forms. The test is more swollen than in any specimens of either of the two species named ; in shape they are quite orbicular and the four genital pores are very large (the posterior being absent) ; in the two smaller specimens the actinostome and anus are exceptionally large ; the internal calcareous connections between the upper and lower surfaces are more complicated than in L. depressum, but do not extend to half the distance from the periphery to the centre as in normal L. decagonale (v. figs.). 12. ARACHNOIDES PLACENTA Agass. Arachnoides placenta, L. Agassiz, Monogr. d'Echinod. ii. 1841, p. 94. Reference. Alexander Agassiz, Revision of Echini, pt. 3, 1873, p. 530. Locality. Singapore, one specimen between tide-marks. Distribution. Mergui Archipelago, Burma, E. India Is., Australia, and N e w Zealand. Transverse diameter 64 m m . Diameter in plane of odd ambulacrum 65 m m . 13. ECHINODISCUS L.EVIS Agass. Echinodiscus Icevis, Alexander Agassiz, Revision of Echini, pt. 3, 1873, p. 533. Lobophora truncata, L. Agassiz, Monogr. d'Echinod. ii. 1841, p. 66. Locality. Singapore, three specimens between tide-marks ; at low tide they lie just covered by sand. Distribution. S. Africa, E. India Is., N e w Caledonia, China Seas, and Japan. In one specimen the lunule is incompletely formed on one side, the slit not being closed posteriorly; in the others both lunules are complete. This species is very closely allied to E. biforis, from which it is distinguished by the shape of the test, which is relatively longer in the former, and the transverse line of greatest breadth passes close to the apex, being much more anterior in position than in E. biforis; the lunules, also, are shorter. Louis Agassiz's distinction, based on the absence of transverse grooves between the pore-pairs in L. truncata, does not hold good; in one specimen the pore-fields on the right side of the odd (ant.) ambulacrum aud right posterior ambulacrum are devoid of continuous pore-grooves, while on the other pore-fields they are present; the characters first mentioned are also so variable, that it is quite possible that we are really dealing with a single species1. i Dr. Hanitsch has sent m e an example of this species obtained at Malacca. |
