A Field Guide to the Snails of Lord Howe Island

7 Land snail identification Three main groups of terrestrial land snail are found on Lord Howe Island: Caenogastropoda, Neritimorpha and Pulmonata. The caenogastropods and neritimorphs are only represented by three families, all of which are small snails with an operculate shell and a single set of optical tentacles with eyes at the bases. An operculum , which is a small calcified door that can be used to seal the aperture, is only present in these three families on Lord Howe Island (Figure 1). The third major group, the Pulmonata, contains most of the diversity and is represented by 9 families of endemic species and 11 families of introduced species. There are three main body forms present on Lord Howe Island: snail, semislug or slug (Figure 2). A snail is defined as having a complete shell into which it can retract its entire body. A semislug has a shell which is reduced, usually ear-shaped, and which it cannot retract its entire body into. Semislugs usually have well-developed mantle lobes (which lie over the body) and lappets (which lie over the shell), which are used as additional gas exchange surfaces (see Fig. 10). A slug has a fully internalised or absent shell. Lord Howe Island endemic pulmonates are mostly snails, with two Figure 2. Body forms: Snail, semislug and slug. Figure 1. Operculum. A. Snail with operculum closed. B. Crawling snail viewed from behind, with open operculum sitting on tail.