128 NORTH AMERICAN DIPTERA. 



3. Cheeks broader than the long diameter of the eyes ; oral border mod- 



erately protuberant ; eosta somewhat spinose. . A CTOUA Meigen. 



Cheeks not broader than the long diameter of the eyes; oral margin 



very prominent ; costa bare DRYOMYZA Fallen. 



4. Hind femora long : second antennal joint much elongated, longer than 



the third. .5 



Hind femora only moderately elongated and but little thickened ; second 

 antennal joint as long or a little shorter than the third. 



TETANOCERA Latrcille. 



5. Hind femora thickened; face not produced downward. 



SEPEDON Latreille. 



Hind femora not thickened ; face much produced downward (Central ? 

 and South America). THECOMYIA Perty. 



so. PHYCODROMIM;. 



Pleurae, scutellum and abdomen flat. Front bristly ; cheeks 

 and face bristly, the vibrissae indistinctly differentiated. Legs 

 stout, all the tibiae spurred and with a preapical bristle on the 

 outer side; metatarsi not abbreviated; terminal joint of all 

 the tarsi incrassate and without claws. Neuration of wings 

 complete ; auxiliary vein distinct in its entire course ; costa 

 without bristles ; basal cells not small. 



But a single genus of this family is known to occur in 

 North America, Coelopa Meigen. Members of it are found in 

 great abundance among sea-weed and other algae thrown up 

 by the waves along the sea-shore. 



si. SCATOMYZIM:. 



Tegulae small, the upper one concealing the lower one. 

 Head rounded, eyes round, bare, broadly separated by the 

 front in both sexes. Wings large ; auxiliary vein always pres- 

 ent, the costa never with bristles at its termination, three 

 basal cells always present ; first posterior cell never narrowed 

 or closed. Abdomen with more than four segments. 



The flies of this group are easily confounded with the 



