272 MR. F. P. BEDFORD ON MALAYAN ECHINODERMS. [Mar. 20, 



Dr. B. Hanitsch, Curator of I he Baffles 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. Bidley 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. 



Prom 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 the 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. 



on' 



I. ECIIINOIDEA. 



The region under consideration lies close to the Equator, between 

 the Indian and Pacific Oceaus, and might be regarded as a 

 probable specific centre for many tropical forms whence migration 

 took place in all directions — westwards to the Bed 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, in the 

 case of closely allied species their areas of distribution often 

 overlap : e. g., among Cidaridae, Rhabdocidaris annulifera and 

 R. baculosa ; among Eehinidse, all the species of Salmacis : among 

 Clypeastridae, Eehinodiscus auritus and E. lewis ; and among 

 Spatangidse, Lovtnia elongata and L. subcarinata. 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 depression and Laganum decagonale were frequently 

 dredged together, and must have been subjected to almost identical 

 environmental conditions, and the same is true of Salmacis globator 

 and 8. 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 



