Richard Lydekker, 1911 Encyclopædia Britannica, Volume 13… (1911)
“ To allow space for the hyoid, the sides of the lower jaw are very deep and expanded. The muzzle is projecting, and the profile of the face slopes regularly backwards from the muzzle to the crown. The long tail is highly prehensile, thickly furred, with the under surface of the extremity naked. Howlers dwell in large companies, and in the early morning, and again in the evening, make the woods resound with their cries, which are often continued throughout the night. They feed on leaves, and are in the habit of sitting on the topmost branches of trees. ”
