ene at each posterior córner, one on the postalar callus; the scntellum 

 with four marginal bristles, the posterior pair the longest. 



Legs : — Dark, obseurely yellowish ; the hind tarsi paler ; the hind 

 tarsi moderately expanded. 



Abdomen : Of a rieher velvety black color, the last segment 

 grayish black ; lateral margins with scattered hairs ; on posterior 

 margin of last segment the hairs are bristle-like and at the apex there 

 is a series of eight bristles. 



Wing : — Hy aliñe, with iridescent reflections; length of auxiliary 

 vein (between the humeral crossvein and its tip) much less than 

 distanee between its tip and apex of first vein ; the preangnlar seetion 

 of the fourth vein (between the posterior and apical crossveins) about 

 twice the length of the posterior crossvein. 



Female : — Front moderately broad, the width eqnal to about one- 

 third the length ; the fifth sternite with a group of five erect bristles, 

 the sixth sternite with two bristles. Somewhat smaller in size than 

 the male. 



Three males, one female ; captured while running on the broad 

 leaves of plants in shady woods. 



Type locality : — Quebrada de Lules, Tucumán (2 Febraary, 1927. 

 R. C. Shannon). 



Named for Señor W. O. Thomsen, engineer at the Quebrada de 

 Lules, whose intelligent interest has greatly assisted entomologieal 

 Cüllecting in this favored quebrada. 



Platypeza tucuniana, new species. 



Female: — Similar in size (2.25 mm.) and appearance to the 

 female of P. thomseni. Front more narrow, about one-fourth the 

 length; wing slightly infuscated anteriorly, length of auxiliary vein 

 (between the humeral crossvein and its tip) is equal to distanee 

 between its tip and that of the first vein ; preangular seetion of fourth 

 ^ein approximates the length of the posterior crossvein. 



Six females, taken in the same habitat with P. thomseni. 



Type locality. — Quebrada de Lules, Tucumán, (2 Februarv, 

 1927, R. C. Shannon). 



Genus Ag(il]i(j)¡njia, Verrall 

 Agatho»n/¡a ausiraJis, new species. 



Male: — A slender s))ecies, of average size (3 mm., wing 2.ñ mm.). 

 velvety black, with an iridescent pattern on thorax and abdomen. 



Head : — Ocellar triangle modérate, equal sided and slightly pro- 

 tuberant; eyes very large, reddish (purplish in life) broadly conti- 

 guous above; frontal triangle small, equal to ocellar triangle in size • 

 face black with an iridescent refiection ; antenua modérate, dark, 

 obseurely yellow ; arista long and slender. 



Thorax : — Mcsonotinu covered with an iridescent pattern exeept 

 for a broad median velvely black área which exíends to the anterior 

 but not to the posterior margin ; the bristles are arranged as in P. 

 thomseni, exeept that the posterior mesonotal bristles are a little more 



