Calvert: Odonata of the Neotropical Region. 179 



Genus Oxyagrion. 



The genera Oxyagrion and Telebasis (Erythragrion Selys) are 

 much alike, differing chiefly in the presence of a vulvar spine in the 

 females of the former and its absence in the latter. De Selys has also 

 suggested 22 that in the males of Oxyagrion one or more of the pos- 

 terior abdominal segments are blue, while this is not the case in 

 Telebasis. Of the ten species which he referred to Oxyagrion in 

 1876, 23 three, however (pavidiwi, miniopsis and basale), have no blue 

 abdominal segment, so that this distinction is not very helpful. 



A better character is perhaps furnished by the color-pattern of the 

 thoracic dorsum, which in Oxyagrion never presents any darker mark- 

 ing than brown, while in Telebasis there is always present a dark 

 metallic-green or black stripe or band on each mesepisternum. 



87. Oxyagrion pavidum Selys. 



Habitat : Brazil, Desterro, December, one pair c?9, by H. H. 

 Smith. Carnegie Museum, Pittsburgh. 



^>Z. Oxyagrion terminale Selys. 



Oxyagrion terminate Ris, Hamburg. Magal. Sammelr. Odon. p. 9, fig. 2. 1904. 



Habitat: — Brazil, Rio Grande de Sul, by H. H. Smith, 1 d\ 

 Carnegie Museum. 



Paraguay, Sapucay, December, 1899, by W. T. Foster, 1 d\ 

 U. S. N. M. 



89. Oxyagrion evanescens, sp. nov. 

 (Plate III, fig. 51 ; Plate VIII, fig. 142.) 



d\ Vertex and labrum obscure, blackish or reddish-brown ; traces 

 of a reddish spot on each side a little anterior to the area occupied by 

 the pale postocular spot of allied genera ; frons, clypeus, and antennae 

 red; free margin of labrum, genae, labium, and rear of head yellow. 



Prothorax and thoracic dorsum reddish-brown ; hind prothoracic 

 margin low, convex; sides and ventral surface of meso-metathoracic 

 pale greenish-yellow ; a short black mark at the upper ends of humeral 

 and second lateral sutures. 



Abdominal segments 1-8 red, 1 and 2 yellow inferiorly ; a pair of 

 anteapical dorsal blackish spots on 8; 9 pale (blue?), with a blackish 



22 Bull. Acad. Belg. (2) xlii, p. 956. 

 23 /. c. , xli, p. 291 et seq. 



