For lots of information about lemurs, check out the Duke University Lemur Center. Please consider supporting them - they're doing great work.
The following engravings of lemurs are by
Friedrich Specht and are taken from:
Carl Vogt and Friedrich Specht.
The Natural History of Animals.
Trans. George G. Chisholm.
NY: D. Appleton & Co., 1888.
Volume 1, p. 81. These images are in the public domain. The reprints of them here have been dedicated to the public domain by Creative Commons deed.
Here is a link to a 1024 pixel wide PNG version of the ringtail lemur image above (1.14 Megabytes), and a link to a 1024 pixel wide PNG version of the dwarf lemur image (0.99 Megabytes).
If you have the network resources to host higher-resolution versions of these (anything up to the 66 and 53 Megabyte original scans) as public domain images, and wish to do so, please contact us at: firstname.lastname@example.org