What are the symbols of Saint Jerome?

One symbol of Saint Jerome is the lion.  It is said that Saint Jerome performed a favor upon a lion by plucking or taking out a thorn from the paw of a lion.  The action of Saint Jerome plucking a thorn from the paw of a lion is often symbolized as Saint Jerome being careful and cautious of revealing or uncovering the truth of Christ.  Two other symbols of Saint Jerome are a Cardinal's hat and an aged monk with the Bible.