The crawfish (Decapoda) of Ohio consist of two families (Cambaridae) and (Palaemonidae). The latter has but one species, Palaemon kadiakensis, while the former has three genera (Cambarus, Fallicambarus, Fraxonius [formerly Orconectes], and Procambarus) containing 21 species.
Excellent webpages on Ohio crawfish are cited below. They are important resources for the decapod fancier. There you will find keys to the species of crawfish and shrimp: http://www.crayfishstudies.com/Crayfish_%26_shrimps_of_Ohio.html