Couplet 19

19a:  Mentum with apex deeply emarginate (Figure 26-13A); mid coxal cavity closed laterally; body distinctly flattened dorsally (Figure 26-28C)

Passalidae   p. 411

19b:  Mentum with apex simple, not deeply emarginate (Figure 26-13D); mid coxal cavity open laterally; body evenly convex dorsally (Figure 26-28A,B)