Bestiary

Under the name bestiary comes a medieval book that is a collection of short descriptions of different real or imaginary animals - birds and even rocks that is often accompanied by a moralising explanation. This reflected the belief that the world itself was literally, the Word of God, and that therefore every living thing had its own special meaning. For example, the pelican, which was believed to tear open its breast to bring its young to life with its own blood, was a living representation of Christ. This symbolism was well known at the time - animals depicted in religious paintings were not just animals, they were symbolic of other meanings in the painting.
Bestiaries were popular in the 12th century and were mainly compilations of earlier texts especially the Physiologus.
Very important part of all bestiaries were illustrations. They added a lot to the descriptions, serving then as an educational tool.
The most important of bestiaries of that time is Aberdeen Bestiary.

T.H. White's translation of a medieval bestiary can be found on-line at http://libtext.library.wisc.edu/Bestiary/