Terrestrial molluscs in Nee Soon swamp forest 
115 
areas. It has a tiny shell with distinct ribs on the outer surface. It has a lower spire than 
Liardetia convexiconica and its shell is dull brown. It was found near the outskirts of 
Nee Soon freshwater swamp forest. 
Microcystina sp. 
Microcystina is a tiny snail with a shell width of less than 3 mm. The shell is glossy 
and brownish in colour. Only one taxon within the genus appears to be present within 
Singapore, but it was not attributed a species name by Ho (1995), nor is it here. Only 
three specimens were observed throughout the survey. 
Family TROCHOMORPHIDAE 
Geotrochus lychnia (Benson, 1852), Fig. 2K 
Geotrochus lychnia is a very rare species that was only encountered twice during the 
survey, in both cases only as empty shells. Its shell has a small umbilical opening and 
its periphery is acutely keeled. Singapore is the type locality for Geotrochus lychnia. 
Helicarion perfragilis (von Mollendorff, 1897), Fig. 2L 
Helicarion perfragilis is an arboreal snail that is commonly found in open vegetation. 
The shell is very fragile and breaks easily. It was observed in rather high numbers near 
the outskirts of Nee Soon but none was recorded within the forest. 
Family ARIOPHANTIDAE 
Hemiplecta Humphreysiana (Lea, 1841), Fig. 2M 
Hemiplecta humphreysiana is the largest native snail found in Nee Soon freshwater 
swamp forest and can grow to a shell width of up to 5 cm. The shell is brown with a 
dark brown stripe that runs along the periphery of mature specimens. Although, this 
species is commonly known to be found on algae covered logs and the forest floor 
(Ho, 1995), several individuals were observed clinging on to trees up to more than 2 
metres high. It was observed feeding on fungus on many occasions. Singapore is the 
type locality for Hemiplecta humphreysiana. 
Parmarion martensi Simroth, 1893, Fig. 2N 
Parmarion martensi is a common slug found in many gardens and parks. Only two 
individuals were observed during the survey, at the outskirts of Nee Soon. 
Microparmarion strubelli Simroth, 1893, Fig. 20 
Microparmarion strubelli is restricted to forested areas with a dense canopy cover. 
Unlike other snails, its shell is reduced to a thin plate to which it can no longer 
retract for protection. Black markings are observed on the visceral hump. Only three 
specimens were observed throughout the whole survey. 
