320 THOMAS SAY FOUNDATION 



PLATE 18. 



Genitalia of Perla. 



Fig. 1. Perla bilobata sp. nov. $, ventral view. 



Fig. 2. Perla bilobata sp. nov. 9 , ventral view. 



Fig. 3. Perla bilobata sp. nov. $ , side view. 



Fig. 4. Perla alameda sp. nov. $ , dorsal view. 



Fig. 5. Perla duplicata Bks. $ , dorsal view. 



Fig. 6. Perla duplicata Bks. $ , ventral view. 



Fig. 7. Perla aestivalis sp. nov. $ , ventral view. 



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



Fig. 9. Perla aestivalis sp. nov. eggs. 



Fig. 10. Perla aestivalis sp. nov. $, ventral side. 



Fig. 11. Perla venosa sp. nov. $ , ventral view. 



Fig. 12. Perla venosa sp. nov. $, dorsal view. 



Fig. 13. Perla verticalis Bks. $ , dorsal view. 



Fig. 14. Perla verticalis Bks. $, ventral view. 



Fig. 15. Perla verticalis Bks. $, ventral view. 



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



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



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



Fig. 19. Perla luctuosa Bks. $, ventral view. 



