They belong to the genus ateles, so called because they want the thumb, and are therefore imperfect or unfinished as regards the hands.
"Popular Adventure Tales"
Mayne Reid
But what the ateles want in hands is supplied by another member-the tail, and this they have to all perfection.
"Popular Adventure Tales"
Mayne Reid
In fact, the ateles rarely descend from the trees, which are their natural habitat.
"Popular Adventure Tales"
Mayne Reid