A comparison of two onchidiid species (Mollusca, Pulmonata)

Abstract

Two externally similar species of Onchidiidae (Superfamily Onchidioidea), Onchidium verruculatum and Onchidina australis, occur together at Careel Bay in Sydney, NSW. These species were identified in a study of both external and internal morphology. The alimentary system and reproductive structures were examined and are illustrated. The most obvious external character separating the two species is the position of the pneumostome, which is located posteriorly in the midline in Onchidium verruculatum and to the right of the midline in Onchidina australis. In addition, differences in shape and colour distinguish the two species, as does presence or absence of accessory eyes. Important anatomical differences are the length of the penis and the presence or absence of an accessory penial gland, the number of lobes of the ovotestis and the presence or absence of a crop.

Key words:

• Onchidiidae
• Australia