No. 39] ODONATA OF CONNECTICUT: GOMPHIDAE 1 47 



Ventral margins of terga 8 and g not straight, when viewed from 

 the side but convexly rounded and the margins of 8 and usually 

 9 extending ventrad further than the preceding segments ; the 

 lateral margins of 8 and g not parallel with the margins of 3 to 6 7 



7. Vulvar lamina wider than long ; mesal stripes of mesepisterna not 



connected with mesothoracic collar (Fig. 22, No. 2, 4, 6) 12 



Vulvar lamina decidedly longer than wide ; stripes of mesepisterna 

 connected with mesothoracic collar 8 



8. Lateral margins of the vulvar lamina with a median notch or 



indentation, constricted at one-third their length (Fig. 20, No. 18) 



crassus 

 Lateral margins of the vulvar lamina without a median notch, not 

 constricted at one-third their length 9 



9. Tips of the vulvar lamina directed strongly laterad fraternus 



Tips of the vulvar lamina not directed strongly laterad 10 



10. Tips of the vulvar lamina in contact vastus 



Tips of the vulvar lamina distinctly separated at tips 11 



11. Vulvar lamina half or two-thirds as long as segment 9 . . . (externus) 

 Vulvar lamina less than half as long as segment 9 ventricosus 



12. Abdomen with pale basal rings on segments 3 to 6 ; thorax with 



most of the metapleura infuscated (Fig. 22, No. 6) scudderi 



Abdomen without pale basal rings on segments 3 to 6; thorax with 

 most of the metapleura pale (Fig. 22, No. 4) 13 



13. Metapleural suture with a dark line; dorsal basal spots of terga 



3 to 8 very small notatus 



Metapleural suture without a dark line ; dorsal spots on base of 

 terga 3 to 8 elongate and with a tendency to form stripes on the 

 dorso-meson amnicola 



14. Mesepisterna pale with darker stripes, more than half dark 15 



Mesepisterna dark with pale stripes, more than half pale 18 



15. Occipital ridge depressed at center (Fig. 21, No. 21) borealis 



Occipital ridge not depressed at center 16 



16. Occipital ridge usually with a denticulate spine at middle . . .villosipes 

 Occipital ridge without a denticulate spine at middle 17 



17. Transverse ocellar ridge not as long as the anterior margin of the 



occiput and not as long as the transverse line connecting the 



outer (lateral) margins of the two lateral ocelli furcifer 



Transverse ocellar ridge as long as the anterior margin of the 

 occiput and as long as the transverse line connecting the outer 

 (lateral) margins of the two lateral ocelli pallidus 



18. Length of the abdomen not over 31 mm exilis 



Length of the abdomen more than 31 mm 19 



19. Each plate of the vulvar lamina longer than wide (Fig. 20. No. 7) ; 



without a broad median notch between the two plates 20 



Each plate of the vulvar lamina shorter than wide (Fig. 20, No. 



S) ; with a broad median notch between the two plates 23 



20. Occiput as in Fig. 21, Nos. 19, 21, the ridge depressed at center .. 21 

 Occiput as in Fig. 21, No. 20, the ridge not depressed at center .. 22 



21. Pale stripe of the mesepisterna more than half the width of that 



sclerite; metepisterna heavily infuscated; occiput as in Fig. 21, 



No. 19 descriptus 



Pale stripe of the mesepisterna less than half the width of that 

 sclerite; metepisterna not heavily infuscated; occiput as in Fig. 

 21, No. 21 borealis 



22. Occipital ridge nearly straight; a pointed tubercle laterad of each 



lateral ocellus ; length of abdomen 28 to 32 mm exilis 



Occipital ridge elevated at center; pointed tubercle beside each 

 lateral ocellus usually absent ; length of abdomen 33-36 mm. spicatus 



