68 



usually 2 or 3, broad aud subtruncate, separated by 



deep narrow incisions ; side margins of 9 entire, often 



fringed with soft hairs, as in .4.1, 10 not longer than wide. 



ii Dorsal hooks very small, pointed on 6 to 9; lateral lal)ial 



lobes 4-toothed. 14. exilis. 



i. Dorsal hooks wanting, except usually a distinct median 



tooth in the hind margin of 9; a fine smooth median 



abdominal line; labial lobes rarely more than 3-toothed. 



jj. Length of ventral surface of 9 along median line not 



more than half its width at base. 



kk. Dorsal hooks entirely wanting; lateral spines of 9 



as long as segment 10. 16. sp. (h). 



k. A broad triangular flat dorsal median tooth in the 



hind margin of 9, as long as segment 10; lateral 



spines of 9 twice as long as 10. 17. sp. (c). 



J. Length of ventral surface of 9 more than half its width 



at base; apical hook of anterior tibia? very small. 



{Sfjj/nrns Needh.) 



///. Ventral surface of 9 distinctly shorter than its basal 



width ; lateral spines of 9 about one third as long 



as their distance from the median dorsal tooth of 



the segment; median tooth minute. 18. amnicola. 



II. Ventral surface of 9 about as long as its basal width; 



lateral spines of 9 at least two thirds as long as 



the distance to the median tooth. 19. pJagiatns. 



I. Ventral surface of 9 twice as long as its basal width. 



21. sp'niiceps. 



1. GompliKS sp. (r/). 



Gomphus sp., Hagen, '85, p. 264, No. 17 (nymph). 



This species is known only from a single nymph described 

 by Dr. Hagen from Indiana. It may be distinguished by the 

 following characters: 



Length 30 mm. Lateral lobes of labium with a sharp bent 

 apical hook and ten strong teeth ; median lobe straight ; seg- 

 ment 9 longer than 8, three times as long as 10 ; lateral spines 



