15. a) S3-S6 simple, without lateral foveae or swellings (Figure 27a); S5 with apical margin straight (Figure 28a) ….. Dufourea marginata (Cresson)

b) S3-S6 with lateral foveae or swellings (Figure 27b); S5 with apical margin concave (Figure 28b) ….. Dufourea fimbriata (Cresson)

Figure 27a: D. marginata (male), S3-S6 simple, without lateral foveae or swellings
Click to Enlarge →           a

Figure 27b: D. fimbriata (male), S3-S6 with lateral foveae or swellings
Click to Enlarge →           b

Figure 28a: D. marginata (male), S5 with apical margin straight
Click to Enlarge →           a

Figure 28b: D. fimbriata (male), S5 with apical margin concave
Click to Enlarge →           b