s 



57 



joints prismatic or tlatteued, witii the lateral margins acute, distinct. The 

 body is comparatively slender and graceful, l)ut not so linear and phasma-forin 

 as in the preceding group; the posterior femora are not so much enlarged at 

 the base as in the remaining portion of the sub-family, although slightly more 

 so than in the preceding. 



Those who reverse the arrangement adopted here, and consider tlu' 

 passage from the Phasinidce to the Acrldldce as ascending, find in this group 

 some strong arguments in favor of that view, as in some respects, althougli 

 well defined, it is more generalized than any of the following groups. Here 

 we find the cylindrical form and elongate conical head approaching the Pro- 

 scojj'ice, but these two characters are no longer united, at least the maximum of 

 each is not found in any one species. Here, too, we find what might be 

 claimed as the initial point, or point of divergence, of the two great branches 

 of the remainder of the sub-family, the (Edipodiform and the Acridiform; 

 starting with the smooth presternum, we continue with it through Pyrgo-. 

 morpha, Oxycoryphus, Stenobothrus, &c., to the typical ffidipodas; on the 

 other hand, starting at the same point with the tuberculiform prosternal 

 spine in the Opomala, we pass through the Xiphoceridse, to the typical Acridii. 



This, group is represented in the United States by four genera, Tryxalis, 

 Mesops, Opomala, and Pyrgomorpha. 



Synoptical table of the genera. 



A. Prosternum smooth, not spined : 



a. Head elongate-couical, ascending Tryxalis. 



aa. Head shorter than the pronotum, sub-pyramidal, horizontal 



above, or but slightly ascending. _ . ryrgomorplui. 



AA. Prosternum armed with a spine or tubercle : 



a. Pronotum cylindrical ; eyes not prominent Mesops. 



aa. Eyes somewhat prominent ; pronotum usnally distinctly 



tricarinate. Opomala. 



TRYXA1.IS, Chaa'p. 

 Gryllus Acrida, Linn. ; Truxalis, Fabr. ; Troxallis, Fisch. d. W. 



Body elongate, slender. Head ascending obliquely in the form of an 

 elongate cone ; face very oblique ; eyes elongate oval, very oblique, and 

 placed well forward ; vertex elongate, broad, and more or less tricostate, the 

 margins expanding over the antennal foveola?. Antennae as long or little longer 

 than tile head. In-oad near the base, acuminate at the apex, triquetrous. Pro- 

 notum short, tricarinate; sides parallel or nearly s(j ; posterior margin angled 

 8 A 



