These lovelies are Coleman shrimp, Periclimenes colemani. They are generally found in mating pairs atop the exquisitely beautiful but frightfully poisonous, Fire Sea Urchin, Asthenosoma varium.
The female of the Coleman pair in this photo is the slightly larger beauty on the left. She's looking poised and ready to catch something tasty with her open claws. Coleman shrimp and several other fish and invertebrates were named after the Australian naturalist and underwater nature photographer, Neville Coleman. It was his life's mission to document all of the sea life of Australia.