68 DRAGONFLIES OF NORTH AMERICA 
pointed abdomen. The labium is short, the mentum little longer than 
wide, parallel sided. The median lobe is convexly rounded, its edge 
is beset with minute quadrate denticles (a score or more of them) at 
the base of the fringe of scale-like hairs. The lateral lobe is rounded 
on the end, there being no end hook, and the inner margin is beset with 
very numerous minute teeth. 
As nymphs the species are not sharply defined. Such characters as 
have hitherto (1927) been found for distinguishing the known forms are 
given in the following table: 
The Known Nymphs 

. Teeth on Lat. Dorsal Described 
L h 
Buea tds lat. lobe | spines on | hooks by 
aspersus 27 12-15 7-9 2-9 | Ndm. 01, p. 438 
bison 29 14 6-9 2-9 | Kndy. 717, p. 547 
carolinus 26 7-9 2-9 | Hag. ’85, p. 258 
carolus 26 14 7-9 7-9 | Ndm. ’01, p. 439 
colubrinus 23 7-9 2,7-9 | Hag. ’85, p. 257 
morrisoni 28 12-15 7-9 2-9 | Kndy, ’17, p. 548 
occidentis 28 6-9 2-9 | Hag. ’85, p. 259 
severus 28 14 7-9 2-9 | Hag. ’85, p. 259 
rupinsulensis 25 6-9 2-9 | Ndm. & Hart. ’01, p. 60 
KEY TO THE SPECIES 
Adults 
L...P ace.cross.striped with blacks: .....+ <)-taec sheer ia nets anne 2. 
Face not: cross:striped with: blackyniss.. (458: Wteie bak Ope 3. 
2 Expanse 64 mm.; clypeal stripe entire......... colubrinus, p. 70 
Expanse 48 mm.; clypeal stripe interrupted. . ..anomalous, p. 70 
3.0 Tibige yellow-externalliy .nn: Slabeona eines: ss: es > oe eee 4. 
"Prbise blacks Marl de kad 203 et Ts oka oo cee eee 10. | 
4 Stripe 2 sinuous on the front margin........... phaleratus, p. 71 
Stripe 2 straight or gently curved or wanting................ 5. 
5. Stripes 4:dndib wanting. 4 2cuse a0 okths 2. Same ean 6. 
Stripes 4:and:5 presentis’. 1b sxdiveesidis se Jie eee 8. 
6: Stripe'l presente 4493) 2 Re ee eee ri 
Stripe 1 absent: (12°50 a ee an 9. 
7 Hair of thorax above hind coxae white......... occidentis, p. 71 
Hair of thorax above hind coxae brown..............--.--55 8. 
