178 Annals of the Carnegie Museum. 



Legs pale blue ; femora with a superior blackish stripe. 



Wings clear, stigma grayish-brown, its costal edge longest, vein A 

 (= inferior sector of the triangle of de Selys) separating from the 

 hind margin at (85 per cent, front wings, 70 per cent, hind) or distal 

 to (30 percent, hind wings) the cubito-anal cross-vein (= basal post- 

 costal vein of de Selys); front wings with 9-10 postnodals, 9 more fre- 

 quent ; hind wings with 7-9 postnodals, 8 most frequent ; M 2 (= nodal 

 sector of de Selys) arising nearest the fourth (95 per cent.). The 

 percentages are based on 10 males. 



Abdomen 23.5-24.5 ; hind wing 14-16 mm. 



One male has a blackish spot on the middle of the nasus ; an ill-de- 

 fined blackish spot on the lower part of the mesepimeron, confluent 

 with the lower end of the black humeral line, and the black on abdom- 

 inal segment 3 prolonged forward to within one-fifth of the length of 

 the segment from the base as a narrow stripe very acutely pointed 

 anteriorly. The ventral side of the thorax is pruinose, so that these 

 additional black markings are perhaps accompaniments of age. 



One other male shows traces of pale postocular spots ; possibly in 

 this species there is an ontogenetic disappearance of these spots as in 

 Hesperagrion heterodoxnm (Selys) of Mexico. 20 



?. Unknown. 



Habitat : — Brazil, Cuyaba, 4 $ and parts of 8 others ; Cuyaba, 

 lakes, January, 1886, part of 1 cJ 1 ; Cachoeira Cuyaba, flooded campo, 

 January 26, part of 1 d\ no. 13 ; all by H. H. Smith. Carnegie Mu- 

 seum, Pittsburgh. 



Skiallagma simulacrum shows an extraordinary resemblance in form 

 and color to Acanthagrion chh'ihuanum, a resemblance which has 

 suggested the specific name here proposed. It differs from that 

 species at once in the shape of the abdominal appendages and in the 

 absence of pale postocular spots. 



From the description of the only other known species of Sh'allagma, 

 S. baueri Forster, 21 S. simulacrum differs in the greater extent of blue 

 on the face, prothorax, meso-thoracic dorsum, and abdominal segment 

 3 ; the shorter superior and the longer (relatively to the superiors, at 

 least) inferior abdominal appendages. 



20 Cf. Biologia Centrali-Americana, Neuropt. , p. 103. 



21 Insekten BSrse, xxiii, p. 15, 1906. In that description, second column, 4th 

 line, for " Thorax" read "Abdomen." 



