Here's why:
* New World monkeys (found in the Americas) have a prehensile tail (a tail that acts as a fifth limb), side-facing nostrils, and a wet, hairless nose called a rhinarium. This wet nose helps them smell and taste more effectively.
* Old World monkeys (found in Africa and Asia) have downward-facing nostrils and a dry, hairy nose.
So, the answer is New World monkeys.