50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



PLATE 6 



Fig. 18. Flexible zone. (Magnified 35 diameters. Photographed with 

 Zeiss apochromat 16.) 



gi, Marginal vein. 



si. Notch. 



laa, First depressed (concave) fold of the anterior region; auxiliary vein. 



Iba, Crest of first raised (convex) fold of the anterior region. 



Ilaa, Second depressed (concave) fold of the anterior region. 



Illba, Crest of third raised (convex) fold of the anterior region. 



lam, First depressed (concave) fold of the middle region ; discoidal vein. 



Ilbm, Crest of second raised (convex) fold of the middle region. 



Ilap, Second depressed (concave) fold of the posterior region; anal vein. 



Fig. 19. Anterior portion of the flexible zone. (Magnified 120 diameters. 

 Photographed with Zeiss apochromat 16, Ocular 6.) 



laa, Auxiliary vein. gi, Marginal vein. si. Notch. 



