FOSSIL INSECTS FROM COLORADO. 173 
Upper side of quadrangle longer than inner ; upper and lower sides of 
stigma subequal; base of subquadrangle (hind wing) nearly (a small 
fraction basad) even with the midmost point between antenodal 
cross-veins* ; anterior cross-veins far apart, the cell they bound being 
over four times as long as deep, much as in the living LH. segnatum 
and fischert; Cu, having its origin and course entirely as in Hnal- 
lagma (consequently not as in Telagrion). 
This will not go in either of Kellicott’s divisions (‘Odonata of 
Ohio,’ p. 82), since both bands and spots referred to are wholly 
absent. So far as the colour of the abdomen goes, the species 
should be placed in Amphiagrion, but the generic characters of 
the tenth abdominal segment remain unknown. Icannotsee any 
postocular spots or band, but am not quite positive that these were 
absent. The size agrees better with Hnallagma than Amphiagrion. 
Regarded as an Enallagma, the fossil would come nearest, by 
its coloration, to the little group of E. signatum, fischeri, and pollu- 
tum, and it is noteworthy that it also falls here by the shape of 
the cell bounded by the antenodal cross-veins. (H. civile, hageni, 
and carunculatum have this cell much shorter.) 
The cells between the quadrangle and the level of the nodus 
are four in the anterior and three in the posterior wings; there 
are four cells between M, and M, before the doubling begins; 
the poststigmatal cells are four in the upper and three in the 
lower wings. The subnodus is very oblique. The brace-vein is 
distinct, and M, is conspicuously angled thereat. The lower side of 
the stigma is broad, bordering a trifle more than one cell; in 
most of the modern species it borders conspicuously less than 
one cell, but in the anterior wings of a female taken by Mr. G. L. 
Garlick at San Geronimo, New Mexico, belonging either to HL. 
annexum or calverti, the stigma is as in the fossil. No doubt the 
longer stigma is a primitive character. 
In my table in Amer. Journ. Sci., July, 1908, pp. 71-72, this 
runs to Agrion mascescens, Scudder, but it is smaller than that 
species, and differs in the position of the base of the sub- 
quadrangle. The difference in size can hardly be sexual, as the 
type of mascescens was a male. There is no doubt that it is very 
close to mascescens, and it may be that the difference is due to 
variation, but it seems preferable to treat it as distinct. The 
abdomen of mascescens is described as colourless. 
Hab. Miocene shales of Florissant, Station 1388, 1908 
(George N. Rohwer). 
Breronipm (Diptera). 
Bibto atavus, sp. nov. 
?. Length about 10 mm.; wings 83; head, thorax, and legs 
black, the dorsum of thorax browner; abdomen dusky ferruginous. 
_* In Amer. Journ. Sci., July, 1908, p. 72, there is a short table relating to 
this character, but by some unfortunate accident ‘ quadrangle ” is printed in 
place of subquadrangle. ; 
