ART. 9 AMERICAN XYLOTINE SYEPHID-FLIES SHANNON 43 



tion of the face below the antennae is flat and in line with the frontal 

 triangle; the keel begins very abruptly and continues as a strong 

 ridge to the oral margin ; thorax black with rather long pile ; abdo- 

 men blackish with large bluish white poUinose spots on sides of 

 second and third tergites, the fourth entirely pollinose ; metasternum 

 divided as in Troyidia. and pilose; stigmatical cross vein present; 

 apical cross vein in line with posterior cross vein; anal vein rather 

 prolonged beyond anal cell. Length, 7 mm. 



Only the type specimen is known. Habitat, Chile. 



Type. — In British Museum. 



Genus TROPIDIA Meigen 



TROPIDIA NIGRICORNIS Philiivpi 



The facial carina is developed as described under OrtJiolophus. 

 Frontal triangle and face, except keel, silvery pollinose, upper sides 

 of face yellowish; hind femur greatly SAVollen, the saw-tooth pro- 

 jection moderate; base of abdomen with large black triangle, the 

 apex extending backward to beyond middle of second tergite; re- 

 mainder of second tergite and the third reddish yellow ; fourth ter- 

 gite shining black with opaque reddish posterior margin; stigmati- 

 cal cross vein absent. 



One male; Chile (A. Faz), Determined by J. M. Aldrich. 



Ty^e.— Santiago, Chile (?) 



TROPIDIA BIVITTATA (Bigot) 



Xylota bivittata Bigot. 



A typical species of TropkUa. Face yellow on the sides ; scutellum 

 black; legs black; abdomen mostly reddish yellow on tergites two 

 and three; fourth with anterior and posterior margins yellow. 



Type. — In British Museum. 



Genus ACROCHORDONODES Bigot 



Genotype. — Acrochordonodes dentipes (Fabricius). 



Acrochordonodes at one time regarded a member of the New 

 York State fauna (under Senogaster coDistockl Williston) as strictly 

 tropical. It is a close relative of the Syritta group. The head is 

 very similar to the Syritta type; the abdomen is constricted at the 

 third segment and the hind femur has an outer apical projection. 



ACROCHORDONODES DENTIPES (Fabricius) 



Stcnogastcr coDistocki AVilliston, Proc. Ainer. Philos. Soc, vol. 20, p. 326, 

 (1882). 



A male and female from Georgetown, British Guiana (H. W. B. 

 Moore), at hand. (Determined by F. Knab.) Special features 



