"What's the difference between the North American porcupine 
and the African porcupine," the society matron asked the 
zookeeper.

"The principal difference is the North American species has a 
longer prick."

This, as you might assume, distressed the matron who 
stormed immediately to the zoo manager's office. The zoo 
manager said, "Ma'am, I apologize for my staff's unfortunate 
choice of terms. What the keeper should have said is the 
North American species has a longer *quill*. In fact, their 
pricks are just about the same size."