2 University of Michigan 



Od. Neotrop. Reg., Ann. Carn. AIus., he describes P. recticar- 

 inatus. Ris, Beit, zur Odonatenfauna von Argentina, Deutsch. 

 Ent. Zeitschr., 1908, describes P. jaergenseni; in Ueber Einege 

 Gomphinen von Sudbrasilien und Argentina, Alem. Soc. Ent. 

 Belg., XIX, 191 1, he describes P. auropictiis, lepidiis, and has- 

 isticns; and in Libellen (Odonata) aus der Region der ameri- 

 kanischen Kordilleren von Costarica bis Catamarca, Archiv fur 

 Naturgeschichte, 1916, he describes longistigma, phyllochro- 

 mus, and pcrptisillits. 



The twenty-three species of the genus Progomphus, while 

 forming a natural and generally easily recognized group, yet 

 show remarkable differences in several characters. Venational 

 differences involving characters generally considered valid for 

 the definition of major groups exist within the genus (crossed 

 or open triangles). In Plate II the wings of three species are 

 shown : in pyginaeus, fig. 5, the triangle of the front wing is 

 open and the anal field is only one cell wide, and in the hind 

 wing there are three postanal cells in both the proximal and 

 distal rows ; in risi, fig. 6, the anal field in the front wing is 

 two cells wide for a short distance both proximal and distal 

 to the level of the triangle, and in the proximal row of postanal 

 cells in the hind wing there are four cells, and three in the dis- 

 tal ; in the unnamed species, fig. 7, the anal field of the front 

 wing is still wider, and in the hind wing there are four cells 

 in both the proximal and distal rows of postanal cells. The 

 change in form of the triangle from a fairly regular three-sided 

 figure to almost a four-sided figure, due to the angling of the 

 distal side of the triangle, may be traced in figures 5 to 7. 



In the. proportion of the tibia and tarsus of the third pair 

 of legs striking dift"erences exist. The difference between 

 I'isi and pygmaeus is discussed below in the description of risi. 

 In joergenseni the third tibia and tarsus bear the same rela- 



