102 6 



If we dra^v any conclusions concerning the character of the whole fauna, 

 we may confidently say, even if convinced that it is but imperfectly known, that 

 it belongs entirely to the Indo-Pacific Fauna. I do not think forms occur which 

 are peculiar to the Gulf of Siam ; if so, they may possibly be some of the species 

 of the Mangrove fauna (e. g. Lucina Dalli m.), but I do not believe even these to 

 be peculiar to the Gulf of Siam, they can without doubt be found also in other 

 similar localities in Indian waters. 



The classification is partly that proposed by Professor P. Pelseneer in 1894 

 in his "Introduction à l'étude d. mollusques"', vv'hich is based on the study of the 

 comparative anatomy of the more minute details of the gills; not that I consider 

 it to be quite satisfactory, but, unfortunately, that is true of all other older systems 

 0Î Ihe Lamellibrcinchiata. I have ventured upon some alterations in his system; for 

 instance, I have not reckoned Psammobia to Mgacea, as he does, but placed it 

 under Tellinacea, to which it belongs more closely, judging from other systematic 

 characters. I have retained Pinna under Pteriidae, to which it most naturally be- 

 longs, and not in the neighbourhood of Ostrea and Lima where Pelseneer would 

 have it. To employ the structure of the gills exclusively as the basis of a classifica- 

 tory system^, without taking other features into consideration, especially the struc- 

 ture of the hinge, is in my opinion absolutely wiong in the case of the Lamelli- 

 branchiata. 



' And afterwards revised in liis "A Treatise on Zoology, ed. by E. Rav Lankestkk, V. Mollusca by 

 1'. Pelskneeh, Loudon, 1906." 



^ Cf. E. L. Rice, "Die systemat. Verwertbarkeit d. Kiemen bei d. Lamellibrancliiaten." Jenaische 

 Zeitschrift f. Naturwissenschaft, 31. Hd , 1898, p. 29. 



