THE SUBFAMILY LIBELLULIN^E. 287 



stigma moderate; fore wings with 11-15 antenodal nervures, the last sometimes not 

 continuous, and 9-13 postnodal nervures, the first two to five not continuous, cells of 

 the postnodal area simple, triangle moderately broad or long, on a level with that of 

 the hind wings, traversed by one to three nervures, the base slightly oblique, followed 

 by three to five rows of cells, generally decreasing, and then increasing, generally one 

 supratriangular nervure, one cross nervure in the lower basal cell, sub triangular space 

 consisting of 2-8 cells, sectors of the arculus rising from a point, and moderately 

 curved at the extremities, the nodal sector waved (often considerably) in the middle, 

 the subnodal much less so, two rows of intermediate cells, frequently increasing to 

 three or even four, before the hind margin ; hind wings rather broader than the fore 

 wings, with 9-13 antenodal and 10-16 postnodal nervures, the first four to six post- 

 nodals not continuous, triangle generally traversed, followed by two to four rows of 

 cells, a supratriangular nervure sometimes present, one cross nervure in the lower 

 basal cell (rarely two), sectors of triangle united at base: anal appendages of the male 

 rather stout, often nearly as long as the last two segments, the lower appendage 

 distinctly shorter ; appendages of the second segment moderately conspicuous. 

 Type Libellula A-macidata, Linn. 



Genus 40. Plathemis. 

 Hagen, New. N. Am. p. 149 (1861). 



Frontal tubercle broad, notched in the middle; eyes contiguous; abdomen rather 

 stout, thickest at the base, especially in the male, and gradually tapering to the 

 extremity, about as long as the hind wings (shorter, and hardly narrowed in the 

 female), segments 2 and 3 carinated, segment 8 strongly perfoliate in female : wings 

 rather short, pterostigma rather long; fore wings with 12-25 antenodal nervures, 

 the last not always continuous, and 8-15 postnodals, the first three to five not con- 

 tinuous, cells of the postnodal area simple, triangle long and rather narrow, about 

 on a level with that of the hind wings, traversed by 1-4 nervures, the base oblique, 

 followed by 4-7 rows of cells, generally decreasing to three or four, and then 

 increasing, one or two supratriangular nervures, one cross nervure in the lower 

 basal cell, sub triangular space consisting of 3-11 cells, sectors of the arculus rising 

 from a point, and gradually curved at the extremities, the nodal sector nearly straight 

 at the base, but much waved in the middle, subnodal sector only slightly waved, 

 two rows of intermediate cells (rarely three) before the hind margin ; hind wings 

 broader than the fore wings, with 10-19 antenodal nervures, the last not always 

 continuous, and 9-14 postnodal nervures, the first four not continuous, triangle 

 traversed by one or two nervures (sometimes reticulated, forming four cells), followed 

 by three or four rows of cells (or four and then three) increasing, a supratriangular 

 nervure generally present, one (rarely two) cross nervure in the lower basal cell, 

 sectors of the triangle united at base : anal appendages of the male as long as the 



