464 TERTIARY INSEUTS OF NORTH AMERICA. 



more or less infumated, the costal margin of tlie coriiim infuscated, and at 

 the apex of the same a large, round, blackish, cloudy spot ; membrane 

 infumated to the same degree as the corium, but the apical two-fifths over- 

 lain by a similar black cloud, which fades a little next the margins of the 

 wing. 



Length, 9"""; breadth of thorax, 5.5°""; abdomen, 6.25'"'". 



Florissant. Two specimens, Nos. 8471, 10405. 



10. MECOCEPHALA Dallas. 



To this genus belongs a single living insect from Uruguay. It is the 

 only genus that seems to have been published in which the head is pro- 

 longed to an equal degree, which tapers throughout, and in which the mid- 

 dle lobe is not surpassed by the lateral lobes. Quite similar in this respect 

 is a fragment from Florissant, which unfortunately consists of the head 



only. 



Mecocephala sp. 



PI. 28, Fig. 8. 



The base of the head, including the large eyes but not the parts 

 behind, is a little more than twice as broad as long, but in front tlie head 

 is prolonged, so that the postocular pai't is as long as the entire breadth of 

 the head. This portion tapers, at first rapidly until it has reached the intra- 

 ocular width, then gradually to the apex, which is scarcely more than a 

 third the intraocular width ; the tip is roundly truncate. At first appear- 

 ance, and as given in the plate, tlie whole seems to be made up of the lat- 

 eral lobes, the middle lobe being in fact very slender but enlarging a little 

 at the apex. The whole is blackish fuscous and the surface of the liase 

 coarsely, of the frontal projection finely, and in both shallowly and 

 obscurely, punctate. 



Length of head, 5""'; breadth, including eyes, 3.5°""; tip of prolonga- 

 tion, 0.65°"". 



Florissant. One specimen, No. 3007. 



