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 E. signatum 

 djid fisclieri ; Cug having its origin and course entirely as in Enal- 

 lagma (consequently not as in Telagrion). 



This will not go in either of Kellicott's divisions (* Odonata of 

 Ohio,' p. 32), 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. I cannot see any 

 postocular spots or band, but am not quite positive that these were 

 absent. The size agrees better with Enallagma than Amphiagrion. 



Regarded as an Enallagma, the fossil would come nearest, by 

 its coloration, to the little group of E. signatum, fischeri, and pollu- 

 turn, and it is noteworthy that it also falls here by the shape of 

 the cell bounded by the antenodal cross-veins. {E. civile, hageni, 

 and caranculatum 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 Mj and Mg 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, andM^ 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 E. 

 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. 



Hah. Miocene shales of Florissant, Station 13 b, 1908 

 (George N. Eohwer). 



BiBiONiD^ (Diptera). 

 Bihio atavus, sp. nov. 



? . Length about 10 mm. ; wings 8| ; head, thorax, and legs 

 black, the dorsum of thorax browner ; abdomen dusky ferruginous. 



-•'- la 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. 



