NON-MARINE MOLLUSCS OF SURINAM. 39 
* 96. OSTREA PARASITICA Gmel. 
Ostraea parasitica, Gmelin, Syst. Nat., 1789, p. 295. 
Ostraea parasitica Gmel., Reeve, Conch. Icon. XVIII, 1873, 
Ostraea, spec. 4. 
Surinam. Dieperink. 
Environs of Paramaribo. van Heurn, 1911. 
Martens, 1873, pp. 213, 218. Surinam. 
Kappler, 1887, p. 205. Surinam. 
Schepman, 1887, p. 161. Environs of Paramaribo, 
Anna Catharina (Mattapica Canal), Post Groningen 
(all subfossil). 
Substracting from these 98 species and varieties in the 
first place the forms, of which the occurrence in Surinam is 
doubtful or not yet fully stated, and secondly those, which 
could not be identified, viz. the Drymaeus (26), Corona (40), 
Lymnaea (57), Neocyclotus? (77) and Cyrena (94)-species, 
we have a total sum of only 78 species and varieties, un- 
doubtfully collected in Surinam. Among these 11 species 
are new to science. 
Our knowledge of the mollusc-fauna of Surinam and 
neighbouring regions is still too little to permit the 
drawing of any important conclusion as regards the geogra- 
phical distribution of the species in Surinam itself and in 
the North-East of South-America. 
The following „Table [” shows the distribution of the 
land- and freshwater- shell-bearing molluscs in Surinam, 
according to our present knowledge. I have divided the 
colony in 5 regions, agreeing with the 5 principal river- 
systems, to which I have added, as a sixth one, the coast- 
region, including also the inferior course of the rivers. 
The species, of which only ,Surinam”’ is recorded as their 
locality, are omitted. 
Table IL shows the geographical distribution of the non- 
marine shell-bearing molluscs, recorded from Surinam. 
Notes from the Leyden Museum, Vol. XXXVI. 
