ODYNERUS. 357 



sharp, its angles dentiform. Post-scutel truncate, but its poste- 

 rior face not so vertical, more oblique, its middle occupied by a 

 transverse creuulated crest; the crenulations blunt. Metathorax 

 triangular, prolonged, convex, with lateral sharp edges, clothed 

 with white silvery pile; the middle occupied by a polished,, punc- 

 tured cavity, not reaching the top, but continued to the post- 

 scutel by a groove. The superior margin of this cavity armed 

 on each side with a very little, compressed, sharp tubercle (or a 

 quite short ridge). The articular valvar of the apex of the meta- 

 thorax each bideutate, the superior tooth of which is prolonged 

 into a long spine. Abdomen very elongate. The first segment 

 longer than wide, funnel-shaped ; with a sort of transverse depres- 

 sion before its margin. Second segment a little depressed bell- 

 shaped, rather long. 



Head, thorax, and 1st segment above, densely cribrose, not 

 quite as strongly as in chichimecus ; the metathorax and the 2d 

 segment quite finely punctured, except on the posterior part of 

 the latter. 



Black, sericeous. Head quite black. Anterior margin of pro- 

 thorax, margins of the tegulse, inferior spines of metathorax, pos- 

 terior margin of scutel, and of the first two abdominal segments, 

 yellow. Often the 4th segment also, more or less marginate. 

 The crenulation of post-scutel, and the two little tubercles of the 

 summit of metathorax finely punctate with yellow. 



Feet black; knees and tibiae outside, in their total length {%) 

 yellow; tarsi ferruginous beneath. Wings hyaline, smoky along 

 the anterior margin. 



% . Clypeus having a quite exceptional form ; square-rounded ; 

 as broad as high, or broader; its superior margin rounded ; the 

 inferior margin quite widely truncate, subcoucave ; its angles 

 blunt, but the inferior extremity of the lateral margin rather 

 swelled, somewhat tubercular. A spot on the mandibles, clypeus, 

 a line under the scape, yellow; flagellum fulvous beneath. 



Reus. a. diff. — This differs from 0. chichimecus, by its larger 

 size, its head as wide as high; its prothorax much wider ; its 

 metathorax much more elongate and triangular, with a smaller 

 cavity and quite small tubercles ; its post-scutel shorter, with its 

 crest placed near the anterior margin ; by its first abd. segment 

 much more elongate, funnel-shaped ; by the 2d, quite finely 

 punctured. — From 0. tepanecus it is sufficiently distinct by its 



