128 TERTIARY INSECTS OF NORTH AMERICA. 



sented in the United States to-day has not yet been found in its Tertiary 

 deposits, and three-quarters of the fossil species belong to a legion essen- 

 tially tropical and two-thirds of whose living representatives occur in 

 America ; to offset this, the two other legions which are peculiarly tropical 

 (and one of them exclusively American) are wholly unrepresented in the 

 American Tertiaries. From what we then know at the present time the 

 relationship of the agrionid fauna of the European and American Tertiaries 

 was not nearly so close as the living faunas of the two countries. (Sep- 

 tember, 1883.) 



Legion PODAGRION de Selys. 



To this legion belong most of the fossil Agrionina of North America. 

 The species here described are the first that have been found fossil. The 

 recent forms of this legion not a very prolific one occur mainly in trop- 

 ical America, though nearly half the genera and about one-third of the 

 species belong to the East Indies and South Africa. The forms here brought 

 to notice are mostly referable to new genera which find their place in near 

 vicinity to the South American types. One species appears to belong to 

 the South American genus Podagrion. The relationship of these fossils 

 may be looked upon as well defined. Their nearest living relatives are 

 inhabitants of Brazil, Venezuela, and Colombia, 



The genera here represented may be separated in the following man- 

 ner : 



Table of the genera of Podagrion. 



Pterostigma not more than twice as long as broad, surmounting less than two cellules ; supplementary 

 sectors few; few pentagonal cellules 2. Podagrion. 



Pterostigma more than twice as long as broad, surmounting several cellules; supplementary sectors 



numerous; many pentagonal cellules. 



Nodal sector arising from the principal at scarcely one-fifth the distance from the nodus to the 

 pterostigma; postcostal area exclusively or almost exclusively rilled with pentagonal cells; 



several supplementary sectors between the median and subnodal sectors 1. Dysagrimi. 



Nodal sector arising from the principal at about one-third the distance from the uodns to the pter- 

 ostigma ; postcostal area with tetragonal and very few or no pentagonal cells; no perfect sup- 

 plementary sector between the median and subuodal sectors 3. Lithagrion. 



I. DYSAGR10N Scudder. 



Dtjsagrion Scudd., Bull. U. S. Geol. Geogr. Surv. Terr., IV, 534 (1878). 



This new type of Agrionina belongs to the legion Podagrion as defined 

 by Selys-Longchamps, having a normal pterostigma, much longer than 

 broad, the median sector arising from the principal vein near the nodus, the 

 subnodal a little further out, and many interposed supplementary sectors. 



