Sea urchins are beautiful and fascinating, whether alive or dead. Some would say delicious, too, but I haven’t sampled them, despite living and working in Japan and Hong Kong for a bit and backpacking solo all over South-East Asia for three months.
You can see the little tube feet between the spines in the pink sea urchin (Holopneustes pycnotilus, sometimes called the thickened sea urchin) above. According to Davey’s A Photographic Guide to Seashore Life, it is confined to NSW between the Richmond River and Ulladulla (south of Sydney). This one is from Flat Rock, just north of where the Richmond River comes out into the sea at Ballina.
The photo below (Heliocidaris erythrogramma?) shows, in the centre, the ‘Aristotle’s lantern‘ – the hard central mouthparts – which the animal uses to scrape off algae for eating.
The red-spined sea urchin (Holopneustes porosissimus, below) is ‘almost always found wrapped up in algal fronds during feeding’ (according to Sea Stars of Australasia and their Relatives, by Coleman).