A Field Guide to the Snails of Lord Howe Island

98 Microcystidae (Tiny glass-snails) The Microcystidae are a group of generally small, glossy snails with their greatest diversity in islands of the Pacific Ocean. Some species are found in southeast Asia. In Australia, this group shows great diversity on Lord Howe Island and Norfolk Island, but on the mainland is only represented by a few widespread species that are probably introduced. There are probably around 300 species worldwide. Previously this group was included within the Helicarionidae. It is currently regarded either as a separate family or as a subfamily of Euconulidae (Bouchet et al., 2017). Microcystids are small to medium-sized snails with shells of 4-20 mm in diameter. They are characterised by a smooth, glossy shell with microsculpture of incised spiral grooves and a rounded to angulate periphery, but a few heavily ribbed species are known. The animal has a tail with a caudal horn, and the shell lappets (where present) are narrow and finger-shaped. These snails are ovoviviparous, and eggs are laid singly some days or weeks apart and hatch right away. Microcystids are generally arboreal or litter-dwelling. Two genera are present on Lord Howe Island, Innesoconcha and Melloconcha . They are very similar, but members of Melloconcha are generally smaller and their left shell lappet is reduced or absent. Several similar-looking, small glossy species have been introduced to Lord Howe Island, but these all have an open umbilicus and this allows them to be distinguished from the imperforate microcystids. Microcystid shells Innesoconcha A. I. aberrans B. I. catletti C. I. princeps D. I. segna Melloconcha E. M. delecta F. M. flavescens G. M. grata H. M. prensa I. M. rosacea 5 mm