From Valve Cut Content
The Sand Barnacle is an enemy much like the hanging barnacles you would find under bridges in hl1 and hl2, It was to be found in the sands wasteland.
We only have the model and texture for this npc, as no code exists in The Leak.
So In Comparison:
|Npc||trapping method||Hiding method||Attack method|
|Sand Barnacle||Spring loaded tongue whip||Mostly buried in sand||Melee bite attacks when close to centre circle depression|
|Barnacle||dangling Sticky tongue||Attach to ceiling||Melee attacks with mouth when close|