n small earth elemental 

Perception +6; darkvision, tremorsense 30 feet

Skills Athletics +8, Stealth +5 (+7 in rocky areas)

Str +4 Dex -1 Con +4 Int -4 Wis +2 Cha -1

AC  17; Fort +10, Ref +5, Will +8

HP 36

Speed 20 feet, burrow 20 feet; earth glide

Melee [>] jaws +10, Damage 1d8+6 piercing

Earth Glide A living boulder can Burrow through earthen matter, including rock. When it does so, it moves at its full burrow Speed, leaving no tunnels or signs of its passing.

Rolling Charge [>>] The living boulder Strides twice, and can then make a Strike with its jaws. This jaws Strike gains Knockdown.

Bestiary 2, page 108. Expanded in LOIL.