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Placostylus bivaricosus (Gaskoin, 1855)
(Family Bulimulidae)
 Species of Placostylus are found in New Caledonia, Solomon Islands, Fiji, Lord Howe Island and the northern tip of New Zealand. This interesting distribution suggests they probably originated in the old southern continent of Gondwana. These large ground-dwelling snails have very limited distributions and because of their size and biology have been particularly susceptible to the clearing of vegetation and the introduction of farm animals and rats. In New Caledonia, a species found only on the Ile de Pines has been nearly wiped out through relentless harvesting for the restaurants of nearby Noumea.
Placostylus bivaricosus, which is endemic to Lord Howe Island, is considered to have three distinct subspecies, two of which are now considered to be extinct. Shell length to 8cm.
Placostylus bivaricosus bivaricosus (Gaskoin, 1855).
Past distribution
Lord Howe Island. Common over the northern, lower end of the island from sea level to approximately 200m (top of Malabar Hill)
Present distribution
Restricted to three, disjunct populations: Windy Point behind sand dunes; east end of North Bay and 3-6m altitude; east end of Ned's Beach, altitude 30m. All collected in early 1971.
It lives under the litter on the forest floor. It faces threats in all remaining populations from rat predation.
Placostylus bivaricosus cuniculinsulae (Cox, 1872).
Now extinct but previously collected from Rabbit (Blackburn) Island in the lagoon. It has not been collected this century and extinction probably the result of rats and habitat destruction.
Placostylus bivaricosus etheridgei (Brazier, 1889).
Now extinct but collected from the mountains at the southern end of the island, including the Erskine Valley (to 350m). It has not been collected alive since late last century and is presumed to be extinct, probably as a result of rat and pig predation.
Further information
Threatened and Endangered Landsnail species
Meridolum corneovirens | Placostylus bivaricosus | Thersites mitchellae
Dr Rudman | Molluscs Homepage
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