1930 ] 
Notes on American N emestrinidae 
287 
hemispherical. Face flattened or slightly concave. Frons 
flattened; linear or more or less narrowed beneath the 
ocellar triangle in the male (the eyes almost holoptic in 
certain species) ; very broad in the female, often occupying 
about one-third of the width of the head. Eyes bare. Pro- 
boscis elongate, stylet-like, slender, usually directed down- 
ward and backward, more rarely slanting forward ; termi- 
nal labella long and slender, slightly flattened. Palpi short, 
very slender. Antennse short ; the two basal segments sub- 
equal, transverse; the third subcircular, flattened with a 
terminal, three-segmented, bare arista. Ovipositor of 
female long, sabre-shaped, composed of two slender, curved 
valves. Wing: alula broad; apical half never with a net- 
work of cross-veinlets ; branches of third and fourth longi- 
tudinal veins long, running parallel with the hind margin; 
third and fourth veins never coalescing before the margin ; 
first and second submarginal cells separated by a cross- 
vein (Cockerell’s outer radio-medial) ; costa as a rule en- 
closing the hind margin of the wing completely and usually 
reached by the fifth longitudinal (or apical portion of 
diagonal vein), which thus divides the third and fifth pos- 
terior cells; base of fourth posterior cell removed from 
the anal cell and situated at or slightly beyond the lower 
basal corner of the discal cell; anterior cross-vein absent, 
the fourth longitudinal vein usually reaching the third 
some distance basad of the latter’s branching. 
Genotype, by present designation : Rhynchocephalus 
volaticus Williston, 1883. 
Lichtwardt (1907, Zeitschr. Syst. Hym. Dipt., VII, p. 
451) first pointed out that, in the genotype of Rhynchocep- 
halus Fischer ( R . tauscheri Fischer), the upper branch of 
the fifth longitudinal vein does not reach the hind margin 
of the wing. He later (1909) proposed a new genus, Neor- 
hynchocephalus, for the Nearctic R. sackeni and R. volati- 
cus, in which the hind margin is thickened into a vein, 
reached by the diagonal vein. Neorhynchocephalus was 
more fully characterized by Lichtwardt in 1910. 1 About the 
same time and quite independently from Lichtwardt, Cock- 
erell also noticed that the diagonal vein extends to the hind 
margin in R. volaticus, while such is not the case in typical 
Rhynchocephalus. He therefore placed R. volaticus in a 
