1156 
DIPTERA OF AUSTRALIA, 
if it issues from the middle of the fourth longitudinal vein, or a 
little before its middle, it rises in a moi’e or less oblique manner; 
when it issues remote from the middle, it is broken in an angle ; 
if it issues fi’om near the root of the fourth longitudinal vein, it 
rises with a light bend, and then runs in a slightly divergent line 
from the first longitudinal vein until it arrives almost to the 
middle of the wing-disk, and then it proceeds, bent upwards, to 
the marginal cross-vein ; from the latter point it continues and 
joins the costa at or before the apex of the wing ; in this latter 
combination the marginal cross-vein is very small, and is only 
rarely obliquely situated, and if there is an anterior branch to the 
second longitudinal vein this is far retired, and always very near 
the marginal cross-vein. The anterior branch of the fourth 
longitudinal vein issues rarely near the root of the second longi- 
tudinal vein. When the second longitudinal vein issues from the 
middle of the fourth longitudinal, it is at the base coalescent 
with the anterior branch of the fourth longitudinal vein, and the 
third longitudinal vein has its origin a little below, or above, the 
marginal cross-vein, and its fork lies higher up in the wing-disk ; 
in this arrangement of the veins the second longitudinal vein 
is rarely simple, but usually sends out an anterior branch 
which runs into the costa, or into the first longitudinal vein ; this 
branch may be short or long. When the second longitudinal 
vein issues from the base of the fourth longitudinal vein, the 
third longitudinal vein issues at the angle before the marginal 
cross- vein. 
Rarely the anterior branch of the fourth longitudinal vein is 
missing, still more rarely the anterior branch of the third longi- 
tudinal vein ; infrequently one of these branches is, or both are, 
detached at the base. Fifth longitudinal generally only rudi- 
mentary, sometimes entirely missing, but when complete running 
into the posterior margin ; issuing from the root of the fourth 
longitudinal vein. Between the fifth longitudinal vein and the 
fourth longitudinal vein there is a longitudinal fold, beginning 
at the base of the fifth longitudinal vein and appearing like a vein 
