Ground Barnacles are a species of Barnacle indigenous to Xen. They are sessile and remain on the ground, where they excrete acidic compounds to allow them to "burrow" by melting the area beneath them into a pit shape. Their tongues are quite muscular and are held aloft at all times; to avoid detection by would-be prey items, they will most often seek out dark and dank places, where shadows abound. Upon hiding the entirety of their body, they will stop sweating this acidic compound and no longer sink through the ground or floors. Ground Barnacles are related to both Barnacles and Sand Barnacles.
"Ground Barnacles are a species related to the typical Barnacles on Xen. However, instead of attaching themselves to a ceiling they remain on the ground, their tongue trap extending towards the ceiling."
- "The Ground Barnacle was created after realizing numerous alien races I knew about did not have fan-created content yet. The Barnacle was one of the creatures I chose to create, although due to the obvious difficulty of creating a creature that was supposed to sit on the ceiling I made it a subspecies that sat on the ground. Only during the creation of this article did I discover the Sand Barnacle, a creature cut from Half-Life 2 development that might have been intended as a ground-based Barnacle species. Ah well. I decided to include it here since it is an original specimen."