References for Scientific Illustrators
Zoology, Wildlife, Herpetology, and Paleontology
Animals in Motion
by Eadweard Muybridge, Lewis S. Brown
The National Audubon Society Field Guide to North American Reptiles and Amphibians
by John L. Behler, F. Wayne King
National Audubon Society Field Guide to North American Mammals
by John O. Whitaker Jr.
Web Sites:
Online Image Databases 
Animals
Tree of Life Web Project, provides scientific name for species
Google Image Search, searchable database of images