NEUEOPTERA— ODOXATA— .ESCHNINA. 141 



than half as broad, nearly reaching the extremity of the third abdominal 

 segment. The abdomen is equal, scarcely tapering apieally, the joints twice 

 as broad as long, entire, not excepting the last. The caudal flaps or tracheal 

 pads are considerably more tlian half as long as the abdomen, tlie middle 

 one, showing on the left in Fig. 1 0, long, slender, fusiform, pointed apieally, 

 largest a little beyond the middle ; the lateral pair are much larger and 

 asymmetrical, the inner flange, or the portion of the tracheal pad lying 

 within the median rod, being subequal, but broadest just before the tip, as 

 broad throug'hout as the broadest part of one flange of the median flap ; the 

 outer flange gradually expanding with a slight convexity from the base to a 

 little beyond the middle, where it is twice as broad as the opposite flange, 

 and then tapering rapidly, regularly, and with a scarcely perceptible con- 

 cavity, to the tip of the median rod ; the edges of the pads are delicately 

 denticulate, distantly on the expanding basal portions, more densely on the 

 apical tapering parts and especially on the outer edges of the lateral pads, 

 the denticulations, like the median ribs, being black. 



Length of body (excluding terminal flaps), 21""™; of front femora, 

 3.25""" ; middle femora, 3.25'""' ; hind femora, 5"'" ; hind tibiae, 6.25°'" ; hind 

 tarsi, 2 25"" ; wing pads, 6.5"'™ ; breadth of head, 3.5"" ; thorax, 3"" ; base of 

 abdomen, 2.65""; tip of same, 2.P""; length of terminal flaps, 7.5™"; 

 breadth of lateral flaps, 2™". 



In the present state of our knowledge of the larvfe of Agrionidte it is 

 impossible to indicate with any certainty the position of this nymph. The 

 absence of any sign of the mask, too, will remain a difficulty when we are 

 more familiar with the living forms, but the small size of the head and the 

 shape of the antennse and caudal flaps will afford good points for comparison. 



Florissant. Two specimens, Nos. 13525, 14174. 



Tribe ^^SCHNINA Hagen. 



This group of larger Odonata seems to have been less richly endowed 

 with species and genera than the other families both in past times and at 

 present. The most recent study of the group by de Selys, which has just 

 appeared, divides the iEschnida" proper into five genera and twenty-three 

 subgenera, of which ^schna, with more than half the subgenera, embraces 

 more than half the one hundred and fifty known recent species and is cos- 

 mopolitan. It also embraces all the known fossils from the Tertiaries, 



