102 6 
If we draw 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 a l'étude d. mollusques”', which 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 
of the Lamellibranchiata. 1 have ventured upon some alterations in his system; for 
instance, I have not reckoned Psammobia to Myacea, 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 wrong in the case of the Lamelli- 
branchiata. 
1 And afterwards revised in his “A Treatise on Zoology, ed. by E. Ray LANKEesrenr, V. Mollusca by» 
P. PELSENEER, London, 1906.” 
’ Cf. E. L. Rice, “Die systemat. Verwertbarkeit: d. Kiemen bei d. Lamellibranchiaten.” Jenaische 
Zeitschrift f. Naturwissenschaft, 31. Bd, 1898, p. 29. 
