16. S. stroutii.
Differs from last in thinner margin. .08. and narrower costae, 29. which do not become much narrower at the umbillical area; white, brown within. Common on Little Strout's, Strout's, East and West Hawksbills, and Cistern, Keys l951. Plate 21. figs. 1,2." (Maynard and Clapp in Maynard, 1920d:120)