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Show 272 MR. F. P. BEDFORD ON MALAYAN ECHINODERMS. [Mar. 20, Dr. E. Hanitsch, Curator of the Raffles Museum, for the great amount of trouble he took on our behalf, and for the readiness with which he placed his valuable experience of the local marine fauna at our disposal. I also wish to thank Mr. H . N . Ridley for his kind hospitality and advice. Professor Bell has been good enough to allow me a room in the Natural History Museum, where I have had an opportunity of comparing our specimens with those in the National Collection; and Professor Minchin has kindly given me every facility for microscopical study at University College Laboratory. From the point of view of the geographical distribution of the littoral fauna, this comparatively unworked district is a peculiarly interesting one : the sea rarely reaches a depth of more than 40 fathoms, and never, so far as I know, of more than 80, so that dredging from a small sailing-boat was always possible in calm weather; and although tbe collection of Echinoderms cannot be considered complete, yet I think specimens of all the commoner indigenous species have been collected either by ourselves or obtained from the natives. Professor Bell has kindly looked through this paper and given me valuable suggestions. I. ECHINOIDEA. The region under consideration lies close to the Equator, between the Indian and Pacific Oceans, and might be regarded as a probable specific centre for many tropical forms whence migration took place in all directions-westwards to the Red Sea and East Coast of Africa; northwards to China and Japan; eastwards through the Pacific Islands towards the American Coast, and southwards in the direction of Australia and New Zealand. Plausible as such a view may appear a priori, the Echinoid evidence in its support is very meagre, and seems rather to point to a separate "centre" for each form-unit. The distribution of tropical Echinoids is as a rule very extensive: moreover, iu the case of closely allied species their areas of distribution often overlap: e. g., among Cidaridse, Rhabdocidaris annulifera and R. baculosa ; among Eehinidae, all the species of Salmacis ; among Clypeastridse, Echinodiscus auritus and E. Icvvis; and among Spatangida;, Lovenia elongata and L. subcannata. In these cases where there are no geographical barriers we should expect perhaps a physiological isolation to manifest itself in differences of mode of life and habitat, but such does not seem by any means an invariable rule : Laganum depressum and Laganum clecagonale were frequently dredged together, and must have been subjected to almost identical environmental conditions, and the same is true of Salmacis globator and S. sulcata. Considering the limited area, the Echinoid fauna is a fairly large one. This is no doubt partially to be accounted for by the great variety exhibited by the inorganic environment: near the |