626 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.48. 



which are green against the eyes; a triangular greenish yellow spot, 

 surrounded with black, in front of each antenna and on the frons in 

 front. 



Prothorax. — Male and female. Above dark shining green; sides 

 brown, darker against the green, paler below; beneath pale flesh; 

 hind lobe low, convex. 



Thorax. — Male and female. Dark shining green above, including 

 the mesepisternum and mesepimeron and the upper end of the mete- 

 pisternum; a very short and narrow superior brown humeral stripe; 

 sides below the green area very pale brown, almost flesh, passing into 

 pale flesh beneath; the pale area of the metepisternum more or less 

 definitely edged with dark. 



Abdomen. — Male. Above black, the basal segments with green 

 reflections; obscure, scarcely evident brown basal rings on 3-7; 

 apical articulation of 7 pale; apical third or fourth of 9 pale in life 

 (pale blue?), in dried material dark dull brown; sides dark, shading 

 below into the obscure yellowish brown of the under parts; append- 

 ages black. 



Female. Similar to male; pale area of sides more extensive (dor- 

 sal black narrower) ; apical articulations of 7-8 pale. Genital valves 

 slightly exceeding 10, the long slender palpi reaching the end of the 

 conical appendages which are shorter than 10. 



Legs. — Male and female. Coxae and bases of femora pale flesh, the 

 femora shading apically into pale brown, black at the extreme apex; 

 tibiae and tarsi pale, joints dark. 



Wings more or less slightly tinged beyond the arculus or nodus; 

 in one case with milky reflections; stigma very dark brown, almost 

 black. 



Described from 5 males, 1 female, Wismar, British Guiana, January 

 30 and 31, 1912; 2 males, Tumatumari, British Guiana, February 9 

 and 11, 1912; and 3 males, Potaro Landing, British Guiana, February 

 10, 1912. Type, a male and allotype, a female from Wismar, in my 

 collection. The name refers to the shape of the terminal abdominal 

 plate of the male. 



Paratype. — Cat. No. 19215, U.S.N.M. A male from Wismar, 

 British Guiana, January 31, 1912. 



Between Wismar and Christianburg is a small stream flowing into 

 the Demerara River and crossed by the footpath between the two 

 towns. In the afternoon the backward flow of the river due to tides 

 makes this stream almost unwadable near its mouth. We were 

 attracted to this muddy, log-choked creek by the beautiful Diastatops 

 dimidiata, which we found nowhere else. The banks of the creek are 

 generally covered with impenetrable brush and the exposed margins 

 are slippery and treacherous, due to the rise and fall of water over 

 them. At places logs are piled so indiscriminately in the creek that 

 progress is slow and difficult; and at places the overhanging bushes 



