310 THOMAS SAY FOUNDATION 



PLATE 10. 

 Genitalia of Perlodes and Isogenus. 



Fig. 1. Perlodes signata Hag. $, dorsal view. 



Fig. 2. Perlodes vagans Smith. $ side view. 



Fig. 3. Perlodes signata Hag. $ , dorsal view. 



Fig. 4. Perlodes bradleyi Smith. $ genital hook on tenth abdominal 



tergite. 

 Fig. 5. Perlodes americana Klap. $ genital hook on tenth abdominal 



tergite. 

 Fig. 6. Perlodes signata Hag. $ genital hook on tenth abdominal 



tergite. 

 Fig. 7. Perlodes irregularis Bks. $ genital hook on tenth abdominal 



tergite. 

 Fig. 8. Perlodes yosemite sp. nov. $ genital hook on tenth abdominal 



tergite. 

 Fig. 9. Perlodes vagans Smith. $ genital hook on tenth abdominal 



tergite. 

 Fig. 10. Isogenus frontalis Newm. $, ventral view. 

 Fig. 11. Isogenus colubrinus Hag. $, ventral view. 

 Fig. 12. Isogenus elongatus Hag. $, ventral view. 

 Fig. 13. Isogenus frontalis Newm. $, dorsal view, penis retracted. 

 Fig. 14. Isogenus frontalis Newm. $, dorsal view, penis extruded. 

 Fig. 15. Isogenus frontalis Newm. $ , side view. 

 Fig. 16. Isogenus frontalis Newm. $ supra-anal process and lateral 



stylets. 

 Fig. 17. Isogenus elongatus Hag. $ supra-anal process and lateral 



stylets. 

 Fig. 18. Isogenus colubrinus Hag. $ supra-anal process and lateral 



stylets. 



