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Family  Donacidae

Wedge Shells

The Donacidae is numerically a medium-sized family of bivalves which live on open coast sandy beaches. In NSW there are only three species, Australia-wide there are seven species, and worldwide about 100 species (Huber, 2010).

Wedge shells are prominent in the surf zone in NSW where they burrow shallowly and are often washed out by waves. They are fast burrowers and can rapidly re-burrow when dislodged from position. They are a prominent component of coastal fauna, often so abundant that they are collected for food or bait.

Family Reference

The Australian species were documented by Lamprell & Whitehead (1992). The present work builds on that treatment by updating the nomenclature and synonymy.

Coverage

The three species that occur in NSW are detailed here.

Identification Notes

Shell form

Wedge shells are generally described as triangular, which is so for two of the three species in NSW, but the third is so elongate that the triangular form is not the dominant character. Shells are solid, with weak sculpture with thin or absent periostracum and muted colouration.

Hinge and ligament

The hinge of Latona deltoides is shown in Fig. 1.  In the right valve there is a massive, bifid cardinal tooth that fits between two much smaller cardinals in the left valve. Beside the cardinal teeth there are nymphs to which the ligament is attached; the nymphs are separated in the right valve but joined to the cardinal tooth in the left valve. Widely separated lateral teeth are present in both valves. The ligament is in two parts; one part is attached to the nymphs, while the second part lies in a groove that extends over the dorsal area of the shell.

Shell Interior

The muscle scars and pallial line within the shell may be distinct or indistinct. When visible, the pallial sinus is seen to be large, reaching almost to, or past, the midline, depending on species.

Fig. 1 Hinge teeth of Latona deltoides (C.74250)