References

Bartsch, Paul. 1968. Mollusks. Dover Publications, Inc.. New York, NY.

Gillis, Rick and Haro, Roger J.. 2010. Zoo lab: a website for animal biology. Accessed 7 December 2011. <http://www.bioweb.uwlax.edu/zoolab/index.htm>

Mordan, Peter B. and Fitzgerald, Kevin F.. 2004. Pulmonata (lung-bearing snails and slugs). Pages 411-417. Michael Hutchins, editor. Grzimek's animal life encyclopedia volume 2: protostomes. Gale Group Inc. Farmington Hills, MI.

Unknown. 1985. Mollusks. Pages 250-273. Dr. Keith Banister and Dr. Andrew Campbell, editors. The encyclopedia of aquatic life. Facts on File Publications, New York, NY.

Unknown. 1975. Pulmonates. Vera Fretter and J. Peake, editors. Academic Press, Inc.. New York, NY.

 http://spinner.cofc.edu/~fwgna/species/planorbidae/h_trivolvis.html?referrer=webcluster&