This is not a complete list of all the books in the system that may be helpful--but it provides a good start! Books with an "R" in front of the call number (the Dewey Decimal Classification number) may be checked out overnight only. Books without the "R" may be checked out for the regular three week period.
Grzimek's Student Animal Life Resource by Grzimek's Student Animal Life Resource is an authoritative, comprehensive reference on animal life. The print copy is available in the library, but the online version is available 24/7 through the library catalog.
Be careful--the term planaria is not in the index; however planaria are included in the volume Corals, Jellyfish, Sponges, and Other Simple Animals under the class of Turbellarians.
This volume and others also include articles on regeneration in acoels, crown of thorns, sea lilies and feather stars, and sea stars (starfish).
North American Seashore Creatures by 
The Encyclopedia of Aquatic Life by 