16 ' PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
1 apical, 2 lateral (1 small), 1 discal (far apart); sternopleural 2, 1. 
Calypters brown, with blackish margin. 
Abdomen wholly black, the second and third segments with violet 
reflections; second segment with only one or two appressed marginals 
at side; third with erect row of 12 slender marginals; fourth with 
row of 12 discals not so large, and as many marginals still smaller. 
Legs black, still a little indication of yellow underneath on apical 
fourth of all the femora; tibiae with rather long bristles. 
Wings with slight brown tinge, anterior cross vein infuscated; fourth 
vein curved backward before the bend, so the first posterior cell is 
very wide in this part; it ends a little before the apex, widely open. 
Length, 8.8 mm. 
Type.—Female, Cat. No. 22054, U.S.N.M. 
See note on Somomyia xanthorrhina Bigot at end of paper. 
MESEMBRINELLA TIBIALIS, new species. 
Male.—Head and its members yellow, the back, however, black 
except below inside the metacephalic suture; eyes nearly contiguous, 
separated by only the width of the front ocellus; parafacial very 
narrow, half as wide as the third antennal joint when viewed from 
in front; bucca one-tenth of head height; third antennal joint slender, 
two and a half times as long as the second. 
Thorax brownish yellow on pleurae, humeri, and edges of dorsum; 
all its bristles stout. Chaetotaxy: dorsocentral 2, 3 (in all cases I 
mention the anterior before the posterior of the bristles); acrostichal 
1,1; humeral 2; posthumeral 1; presutural 1; supraalar 3; intraalar 
2; postalar 2; sternopleural 1, 1; scutellum with 1 apical, 2 lateral, 
1 discal (each side). Calypters rather brownish. 
Abdomen narrowly yellow at base above, below yellow nearly to 
apex; second and third tergites violet on apical third, but this is not 
sharply divided from the color preceding it as in some species; first 
and second with only a lateral bristle, third with a marginal row of 
eight stout and erect, fourth with a discal row of eight and a mar- 
ginal of about the same, all strong; fifth tergite visible as a distinct 
crescent at the base of the genital segments, the latter not prominent. 
Coxae and femora yellow, all tibiae blackish, the front ones less 
so, all femora infuscated at tip. 
Wings uniformly brown in color, hind cross vein oblique; fourth 
vein with rounded curve, at the extreme tip slightly recurved. 
Length, 8.7 mm. 
One male, Porto Bello, Panama, March 18, 1911 (August Busck). 
Type.—Male, Cat. No. 25247, U.S.N.M. 
MESEMBRINELLA PURPURATA, new species. 
Male.—Like tibialis in almost every respect but lacking the anterior 
acrostichals and having a heavy subcostal brown stripe in the wing, 
