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subcostal cross vein shortly anterior to its tip. The first longitudi- 
nal vein reaches as far as opposite the distal end of the discal cell. 
The przefurca arises at about the end of the basal two fifths of the 
wing, is straight, not very long, but little more than half as long as 
the remainder of the vein. The oblique upper branch of the 
second longitudinal vein arises directly opposite the tip of the first 
‘longitudinal vein, so that the first submarginal cell is just as long as 
its petiole. The second submarginal is but little longer than the 
first posterior cell. The discal cell is pretty large and nearly as 
long as the posterior cells beyond it. The great cross vein strikes 
it just before its middle. 
This is the largest of the fossil Gonomyie. 
Length of wings, 8.25 mm. 
Florissant, Colorado. One specimen, No. 147. 
Gonomyia primogenitalis. 
BLAS heart: 
In this species the wings are hyaline, without spots or stigma, but 
with fusco-luteous veins. The auxiliary vein ends in the middle of 
the wing, the subcostal cross vein shortly before its tip and nearly 
midway to the base of the przefurca, which, though no longer than 
usual, arises at an exceptionally early point, not far beyond the 
basal third of the wing; it is straight, with no basal arcuation 
whatever, and only half as long as the rest of the vein; indeed the 
whole cellular area of the wing, that is, the region beyond the basal 
cells, is much longer in proportion to the rest of the wing than in 
any of the other species. The first longitudinal vein ends about 
opposite the distal end of the discal cell, and the oblique upper 
branch of the second longitudinal vein arises distinctly beyond its 
tip, though the first marginal cell is longer than its petiole. The 
submarginal is not greatly longer than the first posterior cell; the 
discal cell is rather small and only about half as long as the pos- 
terior cells beyond it, the great cross vein striking it at the end of 
its basal third. The fifth longitudinal vein is scarcely bent at the 
cross vein. ‘The femora are considerably thickened apically. 
The figure on the plate represents only the wing of one of the 
specimens, drawn by the camera lucida. 
Length of wing, 6.5—7.5 mm. ; legs in the smaller specimens: 
fore’ femora, 2-6: tiai.; tibiee, 325° mim: 5 tarsi,.2.475° mm..3" mid 
