Keywords: PortJacksonShark'sEgg20050417c.JPG Egg case of Port Jackson shark Egg case found on Vincentia beach Jervis Bay Territory Australia Egg cases when found washed up on the beach are sometimes known as a Mermaid's purse The screw-like helical flanges help the mother shark to secure the egg within rock crevices User Golden Wattle on http //en wikipedia org en wikipedia page is was here <nowiki> 09 54 24 April 2005 Golden Wattle 2048×1536 642 523 bytes <span class comment > Shark's egg - Port Jackson Shark Egg case found on Vincentia beach en Jervis Bay Territory AYArktos </span> </nowiki> Heterodontus portusjacksoni Egg cases |