I found these 2 nudibranches washed up on Surfers Paradise Beach in Queensland Australia. The larger one is about 35 mm in length. Glaucus atlanticus are often washed up on beaches along with Physalia Jellyfish (a.k.a Portuguese Man Of War or Bluebottle Jellyfish). The reason for this is that Glaucus feed on Physalia and are also at the mercy of the ocean currents and winds.
Glaucus feed almost exclusively on Physalia, and it appears that they are able to select the MOST venomous of Physalia's stinging cells (nematocysts) for their own use. They store the nematocysts in special sacs (cnidosacs) at the tip of their cerata. (Cerata are the fan-like appendages.) So, NEVER touch these guys!!