Occasional Papers of the Museum of Zoology 3 



tion to each other as in pygmaeus. Generally the third tibia 

 and the tarsus without the claws are approximately equal or 

 the tibia is slightly the longer, but I lack sufficient material to 

 study the matter in detail. In risi, however, the hind tarsus 

 without claws is slightly longer than the tibia. 



Under the discussion of risi I also call attention to the great 

 difference in the length of occipital hairs in risi and pygmaeus. 

 The more robust build of risi as compared with pygmaeus is 

 also conspicuous. Within the genus considerable differences 

 in thoracic color patterns exist. Figures 1-3, Plate I, illustrate 

 this. 



Progomphus risi, new species 

 Figs. I, 6, 8, 9, 10, II 



Description : Abdomen, male 26, female 26.5 ; hind wing, 

 male 18, female 21.5. 



Male. — Rear of head brown, paler below, mouth parts light 

 brown ; face brown, marked with leaden or bluish gray as 

 follows : a spot below, not touching the borders, on either side 

 of the labrum ; rhinarium entirely pale ; nasus with a spot on 

 either side, reaching the extreme lateral border; and frons 

 in front above the last yellowish or greenish. Frons above 

 pale, greenish or yellowish, a median posterior ill-defined 

 triangular leaden colored area ; vertex and antennae black or 

 dark brown; ocellary ridge, posterior to each lateal ocellus, 

 well-defined, curved, not angled, at its outer end between the 

 ocellus and the eye ; the two postocellary ridges, one posterior 

 to each lateral ocellus, meeting in the median line almost in a 

 straight line, the angle between them very obtuse ; occiput dark 

 dull green, the posterior edge and adjoining the eyes darker, 

 indentate in the median line from which it rises, on either side, 

 in a very slight concavity to the rear of the head ; hairs on pos- 



