Pye NEW YORK STATE MUSEUM 
of other forms. The one within the discal cell occurs in Hoplolabis, 
Plustomyia [ipl 17) te. 2h Olas lplyZcpanioesslandmassascoiigsia 
others. The one in cell M (the second basal cell, of some systematic 
dipterologists) occurs in Ephelia, Polyangaeus, etc. The one in 
cell M, occurs in Idioplasta. The one in cell At occurs in Discobola. 
The probable significance of all these supernumeraries has already 
been discussed. I consider them lone survivors of a more abundant 
venation. But their widely scattered recurrence inclines me to 
believe in a very remote origin of genera and groups of genera in 
this family. 
And there is among them one that is very peculiar. Apparently 
it is not in the way of disappearing, but of redevelopment. It is the 
one that occurs in Hoplolabis armata in cell rst M*. There 
is here a curious atrophy of the base of M!”, just beyond the first 
fork of the median vein and a creeping of all the vein tips around 
toward the wing apex, and a most curious conformation of the discal 
cell [pl. 23, fig. 5, 6]. It acquires a reentrant angle from which a 
spur starts. These things are foreshadowed in Acyphona [pl. 23, 
fig. 4]. I studied the variability of this spur in some 50 wings of 
this species, and found it to exhibit all degrees of length from a 
complete cross vein down to a spur one third as long, it being usually 
about half as long. This seems to be a relatively new acquisition 
that accompanies the reentrant angle that probably meets some new 
need due to the movements of veins and shift of stresses. 
The median cross vein rarely disappears by the fusion upon it 
of the veins it connects [as in Phalacrocera pl. 11, fig. 2, and in 
Idiophlebia figured by Grinberg in Zool. Aug. 1903. 26:525]. It 
gets curiously reduced in length and reversed in position in Palaeo- | 
poecilostola [ pl. 20, fig. 4]. 
Principal readjustments of venation in the Tipulidae 
We come now to note the correlated behavior of veins and cross 
veins in this family. The principal shifts of veins that clearly show 
correlated movements of many elements of wing structure are tw): 
(1) the formation of the cord and (2) the upshift of veins Cu? 
and M##. Let us consider these somewhat in detail. 
Formation of the cord. As already defined, the cord is the 
principal line of transverse joinings of the veins that traverse the 
wing disk. It is always composed of at least three forks and two 
intervening cross veins. These are the first fork of the radial sector, 
