324 THOMAS SAY FOUNDATION 



PLATE 17. 



Genitalia of Perla 



Fig. 1. Perla hastat a Bks. $ , dorsal view. 



Fig. 2. Perla hastata Bks. 5, side view, penis extruded. 



Fig. 3. Perla hastata Bks. $ , ventral view. 



Fig. 4. Perla expansa Bks. $, ventral view. 



Fig. 5. Pr /'/<( expansa Bks. <$ , dorsal view. 



Fig. 6. Perla expansa Bks. $ , showing the 7th abdominal sternite. 



Fig. 7. Perla erosbyi sp. now $ , side view. 



Fig. 8. Perla erosbyi sp. nov. $ , dorsal view. 



Fig. 9. Perla phalerata Smith $ , ventral view. 



Fig. 10. Perla phalerata Smith, egg. 



Fig. 11. Perla varians Walsh $, ventral view. 



Fig. 12. Perla varians Walsh $ , dorsal view. 



Fig. 13. Perla fugitans sp. nov. $ , dorsal view. 



Fig. 14. Perla fugitans sp. nov. $ , supra-anal process. 



Fig. 15. Perla tincta sp. nov. $, ventral view. 



Fig. 16. Perla modesta Bks. $ , ventral view. 



Fig. 17. Perla modesta Bks. $ , dorsal view. 



Fig. 18. Perla modesta Bks. $ , side view. 



Fig. 19. Perla modesta Bks. $, showing the 7th abdominal sternite. 



Fig. 20. Perla innubila sp. nov. $, ventral view. 



Fig. 21. Perla nona sp. nov. $ , ventral view. 



