ODYNERUS. 177 



The 0. birenimaculatus differs from the 0. Spinolse by its 

 very much more densely punctured and not smooth body, by its 

 transparent wings, by the margin of the 2d segment which is 

 densely punctured, by the first segment which is wider, by its 

 stubbed form, etc. ; from the 0. campestris and unifasciatus by 

 the very much more densely and less coarsely punctured thorax, 

 by the form of the metathorax, by the less coarsely punctured 

 margin of the 2d segment, etc. 



Finally, the 0. birenimaculatus offers a great resemblance also 

 to the 0. renimacula of Europe, although its form is very much 

 more stubbed than that of this last species. 



Bab. New England. New York. 24 ?, 3 %. 



II. The concavity of the metathorax forms no distinct lateral 



angles. 



Here the posterior plate is often rugose. It is at times still 

 bordered at the summit by some ridges or one double arch; 

 sometimes it is not limited, especially not on the sides, where it is 

 effaced and lost in the sides of the metathorax. The concavity 

 is often formed by the meeting of two convex facettes. 



A. Posterior face of metathorax remaining margined, but with- 

 out distinct angles. Body slender, elongate. 



a. Post-scutel strongly truncate. 



21. A. COIlspicilllS Sauss. — Gracilis, niger, ubiqne punctatus; capite 

 et thorace crassissime et rugose punctatis ; prothorace antice cristato, 

 angulato, post-scutello valde truncato, facie postica polita ; inetathorace 

 utrinque baud angulato, foveola lsevi, tenuiter marginata, abdomine 

 dense punctato: prime- segmento minuto, acute suturato ; antennarum 

 scapo subtus, puuctofrontali et subalari, pronoti abdominisque segmeu- 

 torum 1, 2 limbo postico, fascia interrupta scutelli, fascia post-scutelli, 

 lineaque femorum intermedioruui, luteis. 9 • 



Ancistrocerus conspicuus Sauss. Rev. et Mag de Zool.,IX, 1857, 247. 



Total length, 9.5 mm. ; wing, 7 mm. 



?. As slender as a Stenancistrocerus. Head and thorax very 

 roughly punctured. Clypeus very coarsely punctured, finely bi- 

 carinate at tip and minutely bidentate. Head margined poste- 

 riorly. Yertex having a tubercle garnished with an erect brush 

 of hair. Thorax scarcely contracted posteriorly, very square 

 12 



