Gulf Coast spiny softshell turtles, Apalone spinifera aspera (Agassiz, 1857) (Testudines: Trionychidae) from Canoe Lake (33°47′56.16″N, 86°29′25.02″W; Springville, Alabama) and Round Lake (32°41′50.91″N, 87°14′30.39″W; Perry Lakes State Park, Marion, Alabama), were infected by V. robustum Stunkard, 1928, Vasotrema longitestis Byrd, 1939, and Vasotrema rileyae n. sp. The new species differs from its congeners by having papillate suckers, a short testis, an ovary dextral to the oviduct, and a pre-ovarian genital pore that is lateral to the ventral sucker. We studied the newly collected specimens and museum specimens of all congeners to revise the diagnosis of Vasotrema Stunkard, 1926 and redescribe and provide an updated dichotomous key to all species of the genus.