232 THE CANADIAN ENTOMOLOGIST 



parapsidal grooves of mesothorax distinct, entire; width of abdomen 



nearly lyo mm.; wings hyaline, slightly dusky because minutely 



hairy all over, the hairs dark; nervures ferruginous, very distinct; 



costa not bristly; stigma large, about 720 microns long and 320 deep; 



a linear, hardly noticeable, costal cell; basal nervure leaving costa 



very obliquely near base of stigma, its lower part very strongly 



arched, its lower end only about 320 microns in a straight line from 

 subcosta; marginal cell subtriangular, sharply pointed, about 930 

 microns long, its lower side beyond the submarginal cells faintly 

 concave (bulging inward); first s.m. diamond-shaped except for the 

 large part cut off by the stigma, its basal end only a short distance 

 down nasal nervure; first section of radial Or marginal nervure 

 having stigma beyond middle, nearly at right angles; second section 

 nearly obsolete, but marked by the bend in the nervure; second 

 t.c. wholly obsolete, but marked at each end by an angle in the 

 nervure where it should arise; recurrent nervure exactly meeting 

 first t.c; lower end of b.n. basad of t.m. a distance equal to rather 

 more than half of latter; t.m. very oblique; second discoidal com- 

 plete. 



Florissant, in the Miocene shales {Willard Rusk). Type U. 

 of Colorado Museum, 4903. Easily known from the two species 

 described by Brues from the Florissant shales by the obsolete 

 second t.c. Except for this the venation is nearly as in yl. petrina 

 Brues, except that the first section of radius is about as long as 

 second, the marginal cell is narrower apically, the b.n. is strongly 

 bent (straight in petrina), and the second s.m. has its apical corner 

 more produced. The linear costal cell is not different from that 

 seen in other forms in which this cell is described as "absent," be- 

 cause it is not readily seen without a microscope. According to 

 Ashmead's tables, the absence of the second t.c. would throw it in 

 Dacnusinae; but, as Marshall observes, in true Dacnusina? the 

 radius beyond the first section presents an unbroken curve, without 

 any angle where the second t.c. should be inserted. In the meeting 

 of the a.n. and first t.c, A. riiskii resembles Alysia {Goniarcha) 

 atra Hal., but that species has the first s.m. with a broad side on 

 b.n. In the shape of the first discoidal cell, the fossil is suggestive 

 of Dacnusa {Phcefwlexis) petiolata Nees. 



