中
=
丨
+
口
:
Mnemonic symbol: a dart board, because you always try to hit the center.
Julian Giant Squid (zhu-) is throwing dinosaur bones (丨) as darts on a dart board in front of the engine ((e)ng1). To make it a bit more difficult he's throwing mandarins (口) into the air as well and skewers them up right in the center (中 is a mandarin skewered on a dinosaur bone) in mid flight with the dinosaur bones. He's still able to consistently hit the center (中) of the dart board.
山
=
丨
+
凵
:
Mnemonic symbol: 山 looks like the tip of a fork. Sherlock Holmes (sh) is climbing a mountain (山) in front of the anthill (an1). He uses a dinosaur bone (〡) as walking stick, and to have better grip he attached a fork (山) to its tip. Unfortunately he accidentally sticks the fork into a receptacle (凵) on the ground of the mountain and gets shocked.
陵
=
夌
+
阝
:
Li Qingzhao (li), the father of emperor Yao (夌) and the pope (阝) are in a competition over who will have the largest tomb (陵) mound (陵). They are all busy heaping up hills (陵) in the engine's kitchen ((e)ng2).