230 NEW YORK STATE MUSEUM 
The “subcostal cross vein” of many systematic dipterologists 
is not included in this list because it is not a cross vein at all, 
but the free part of Sc? as already pointed out. The basal one 
of these five cross veins, the humeral, is very constant in posi- 
tion and relations, only disappearing by aoe ky when the sub- 
costa, which it braces, atrophies. 
Of the four distal cross veins, the two innermost @ m and m-cu) 
lie between principal veins and effect strong and permanent unions. 
The other two (7 and m) lie in the middle of the principal forks 
of the radius and of media respectively, usually fall outside the 
cord and are far less constant. These two disappear by atrophy; 
the former, only by fusion of veins together, making the joinings 
stronger. The radial cross vein may enter strongly into the forma- 
tion of the cord, as in Conosia |[pl. 21, fig. 5] and the more typical 
Eriopterini [pl. 23] or it may be quite eliminated as in many of 
the Rhamphidiinae [pl. 29] and Paratropeza [pl. 21, fig. 4]. It 
rarely disappears through the fusion of adjacent veins, as in Lechria 
[pl. 10, fig. 5]; more often it is eliminated by fusion from the apex 
backward as in the Cylindrotomini [pl. 15, fig. 4, 5, 6}.. Its posi- 
tion in relation to the forking of the radial sector is very different 
in different crane flies; and in this there prebably lie unused generic 
characters of value. 
The radio-medial cross vein always enters into the formation of 
the cord, being always present or accounted for. It disappears 
only by fusion of adjacent veins upon it. That fusion may be 
brief, as in Rhamphidia [pl. 14, fig. 4] or more extensive, as in 
Ptilogyna [pl. 17, fig. 4], Liogma [pl. 15, fig. 5], Mongoma [pl. 21, 
fig. 6], or Paratropeza [pl. 21, fig. 4], each representing a different 
group, and all highly specialized. It is situated at an unusual dis- 
tance from the base of the wing in Conosia [pl. 21, fig 5], being 
beyond the median cross vein. 
The median cross vein usually lies without the cord (except in 
the case of Conosia, just cited) and when far without, it appears 
to be relieved of great responsibility and tends to disappear along 
with the superfluous branches of the median vein. As a 
rule it disappears in advance of the atrophy of M,;. Owing 
to the upward deflection of the base of M,, this cross vein 
and the deflected portion of that vein equally support the 
tip of M, in very many cases; and either may be eliminated, 
leaving the tip supported on the other. In fact both may go, and 
leave the tip hanging in the membrane unsupported, as illustrated 
