156 



PEOF. E. YON MAETENS ON THE SHELLS 



the ' Boston Journal of Natural History,' vol. iv. 1844, which is the 

 first treatise on the land-shells of that country. Besides Beeve's 

 ' Conchologia Iconica,' several conchological publications by B. A. 

 Philippi have been very useful to me in determining the marine 

 shells, as this author mentions and describes various shells col- 

 lected by his brother, Theodor Philippi, at Mergui, about the 

 year 1846. Descriptions and figures are only given in the few 

 cases of new or very little-known species. In several other cases 

 some remarks are added concerning the more striking and easily 

 observable differences of the species, chiefly if several nearly 

 allied species are mentioned ; they are not intended, however, to 

 give a sufficient description, but only to help the memory of 

 the conchologist in the discrimination of those species. 



Dr. Anderson noted on the spot the conditions under which 

 many of the species occurred ; and his notes I have given verbatim. 

 These are very valuable, as they afford an idea of the circumstances 

 under which the animals live, which are of great importance 

 owing to the influence the surroundings of a species exercise in 

 modifying the general external appearance of the shell, a consi- 

 sideration which is as yet not sufficiently known and appreciated 

 in foreign shells. Many of Dr. Anderson's statements, contained 

 in his notes, coincide with my own observations made during a 

 stay of about two years in the Malayan Archipelago. Chiefly 

 on this account, I have arranged the list into several parts, sepa- 

 rating the land-, freshwater-, and sea-shells, and have even 

 attempted to make a peculiar division for those which live in 

 mangrove-swamps and at the mouths of rivers, as we there find 

 intermingled at the same spot air- and water-breathing mollusca 

 and species of genera which are generally admitted as marine 

 with others of a more fluviatile character. I am well aware that 

 this division of submarine Mollusca cannot be strictly limited 

 either from the marine or from the fluviatile forms ; but it may, 

 nevertheless, be useful to emphasize them in this way, as, 

 otherwise, even the distinction between marine and fluviatile 

 occurrence remains doubtful and arbitrary for some species. 



I have also tried to add, for distinction's sake in italics, a 

 sketch of the geographical distribution of the single species, by 

 naming Uio chief* Localities in which they have hitherto been 

 found ; many of these statements are taken from the collec- 

 tions in the Berlin Museum, the rest from the more reliable 

 condiological authors. If hitherto the "habitat" of the species 



