radial cellule rounded at tip, and at its inferior 

 angle descending to meet the superior angle of 

 the second cuhital cellule, which is triangular : 

 tergum with a transverse groove on the middle 

 of each segment, and a marginal smaller one ; 

 incisures reddish-hrown. 



OBSERVATIONS. 



When traversing the Arkansaw region with 

 Major Long's party, I obtained a single specimen 

 of this insect, which is a male; it is so very 

 similar in general appearance and colour to 

 Cerceris bidentata, Nob. that but for its ge- 

 neric differences, I should almost have been led 

 to consider as a mere sexual variety of that 

 species. But it cannot be placed in the genus 

 Cerceris, as the mandibles are entirely un- 

 armed within, and the second cubital cellule is 

 not petiolated, and the eyes are not emarginated. 



The upper right figure of the plate. 



PLATE 49. 



