ORTALID^ SYSTEMATIC DISTRIBUTION. 63 



Ortalidse a satisfactory distribution in groups, is more apt to 

 insure the recognition within these groups of available genera, 

 than if we should attempt to avail ourselves of affinities, which, 

 although visible to the eye, do not admit of exact definitions. 



Psairoptera finds a fitting location at the end of the Ptero- 

 callina, so as to be immediately followed by the Ulidina. The 

 principal differences from the above-mentioned genera of Ptero 

 callina consist in the posterior angle of the anal cell, which is 

 more or less a sharp right angle, and in the much smaller dis- 

 tance between the end of the auxiliary vein and that of the first 

 longitudinal. The shape of the head likewise shows not unim- 

 portant differences from the other genera of the group, and some 

 of the species of Psairoptera have, moreover, the last antennal 

 joint of a more elliptical shape. 



In enumerating the most characteristic distinctive marks of 

 the Pterocallina, we cannot, for the above stated reasons, lay 

 the same stress upon Psairoptera as upon the other genera of 

 this group. These characters may be summed up as follows : 



Habitus Trypeta-tike ; coloring non-metallic ; head rather 

 broad, but low, with rather protuberant eyes ; face short, per- 

 pendicular, excavated in the middle ; clypeus but little de- 

 veloped ; third antennal joint round or rounded ovate ; thoracic 

 dorsum bristly upon its posterior part only ; third longitudinal 

 vein hairy ; and above all, as the most important character, the 

 unusually large distance between the end of the first longitudinal 

 and that of the auxiliary veins. 



For the Pterocallina from North America, hitherto known, 

 we can add to the above-enumerated characters the posterior 

 angle of the anal cell, which is drawn out in a long lobe. 



SECOND DIVISION. 



ORTALIDJE HAVING THE FIRST LONGITUDINAL VEIN BARE. 



The European genera belonging here are : SEOPTERA Kirby, 

 TiMiAWied., ULIDIA Meig., CHRYSOMYZA Fall., with which 

 Chloria Schin. is coincident, and EMPYELOCERA Lw. They are 

 allied enough to each other to be united in the same group. 



A type, very different from the preceding genera, appears in 

 the genus RICHARDIA Rob. Desv., which seems to be rather 



