144 CONNECTICUT GEOL. AND NAT, HIST. SURVEY [Bull. 



Ventral margins of the superior anal appendages seen from the 

 side with a tooth (Fig. 21, Nos. 15, 18) 6 



6. Superior anal appendages as in Fig. 21, No. 15; occipital ridge 



prominent abbreviatus 



Superior anal appendages as in Fig. 21, No. 18 ; occipital ridge not 

 prominent brevis 



7. Ventral margins of terga 8 and 9 convexly rounded, extending 



ventrad considerably and not in line with the margins of segments 



3 to 6 (Fig. 18, b), terminal segments expanded 14 



Ventral margins of terga 8 and 9 not extending ventrad, noticeably, 

 and in line with the margins of 3 to 6 (Fig. 18, a) ; terminal 

 segments not or very little expanded 8 



8. Abdomen 45 mm. long or more 9 



Abdomen less than 45 mm. long 10 



9. Last three segments of the abdomen reddish brown; superior 



appendages of the male with a lateral angle in dorsal view plagiatus 

 Last three segments not entirely reddish brown; superior appen- 

 dages of the male without a lateral angle in dorsal view ..spiniceps 

 10. Superior anal appendages without sharp teeth on lateral, ventral or 

 mesal surfaces ; without a distinct angle on lateral surfaces when 



viewed from above exilis 



Superior anal appendages with a tooth on either lateral, ventral or 

 mesal surfaces; if without conspicuous teeth, then with- a decided 

 angle on lateral surfaces when viewed from above il 



a Gomphus spicatus bGomphus 



Fig. 18. Last four segments of males of Gomphus spicatus and G. ven- 

 tricosus, showing differences in the structure of segment 8. 



11. Superior anal appendages show a tooth on the venter when viewed 



in lateral profile 12 



Superior anal appendages do not show a tooth on the venter, when 

 viewed in lateral profile lividus 



12. Dorsal view of the superiors shows a tooth on side of each, none 



on the mesal surfaces spicatus 



Dorsal view of the superiors shows teeth on the sides and also on 

 the mesal surfaces 13 



13. Mesal tooth of the superiors sharp borealis 



Mesal tooth of the superiors rounded descriptus 



14. Mesepisterna dark with pale stripes (half, or more than half dark) 17 

 Mesepisterna pale with dark stripes 15 



15. Occiput with a sharp elevation at center villosipes 



Occiput without a sharp elevation at center 16 



16. Hind femora pale pallidas 



Hind femora black furcif er 



17. Dorsal pale stripes of the mesepisterna not connected with the 



mesothoracic half collar 18 



Dorsal pale stripes of the mesepisterna connected with the meso- 

 thoracic half collar 20 



18. Abdomen with basal pale rings on segments 3-6 scudderi 



Abdomen without basal pale rings on segments 3-6 19 



19. Lateral pale stripe of the mesepisterna reduced to a line of dots or 



wanting amnicola 



Lateral pale stripe of the mesepisterna very distinct notatus 



