The Horseshoe Crab - Limulus polyphemus
- Brief profile of species biology and ongoing research, with a photo.
- http://marylandfisheries.fws.gov/horseshoe_crab.htm

Merostomata
- Brief description of the class, from the Animal Diversity Web.
- http://animaldiversity.ummz.umich.edu/arthropoda/merostomata.html