#veneridae

Probably the Rose-Rayed Venus Shell Placamen flindersi.

The genus is found from Australia, north through Indo-Malaya and the Phillipines, to Japan and the Korean Peninsula.

Wedding cake venus (Bassina disjecta)

Endemic to the beachs of southern Australia and New Zealand, from the Eocene to the present.

AKA Venus tasmanica, humphreyi, costulata and gallinula, Feathered Venerid, and Hen Venus.

More often found on SE coastlines, in sand off sheltered ocean beaches, from low tide to depth of about 35m.

AKA Periglypta chemnitzi (a mispelling), Periglypta chemnitzii and originally as Venus chemnitzii.

The first field trip I did with the WA Naturalist's Club after my return from New Zealand last year was a beach walk at Woodman Point - I collected a quite nice variety of seashells, such as these one with its intriguingly serrated edges, which is found on seashores around a fair amount of the Indian, Western Pacific, and Australian shorelines, but doesn't seem to be very common.

That assumes it's actually chemnitzii, though - one of the resources I checked says that we don't get chemnitzii in Australia, and instead have laqueata instead.

Found in shallow waters from the southern half of Australia.

The common name derives from the lifestyle, embedded in soft rock and hardened sediment, rather than any judgement on its nondescript appearance. It's likely that some supposedly related species such as crebrelamellatus are actually the same one, with the shell shaped by the substrate it grows in.

AKA  Cytherea (Artemis) anus, and Dosinia horridus, tuangi-haruru, ringed dosinia, coarse dosinia, or coarse biscuit shell. A common surf clam around the islands of Aotearoa, buried in clean sand down to about 15m depth. The largest and heaviest species in the genus, occasionally exceeding 80 mm in diameter.

Tawera is the Māori name for Venus, and it is indeed a Venerid clam. The genus was named by New Zealand paleontologist John Marwick in 1927, and this species by malacologist H. J. Finlay in 1928. Finlay didn't specify who Marion was in the only paper I could dig up - it turns out Marion Ivy Mary Keys was his wife.

Assuming T. marionae is actually a species.

notaspidea on inaturalist told me, as they gave me the ID, that

"In being ovate-trigonal and coarsely sculptured, this valve corresponds with the Tawera morphotype named T. marionae. However, one character that doesn't match is the internal colouration - Tawera marionae is described as dull white internally. So, whether T. marionae is a species or merely a southern form of T. spissa remains to be tested genetically. The drill holes would have been made by the predatory naticid gastropod Tanea zelandica."