ODYNERUS. 333 



comparing numerous specimens. It seems nearly impossible to 

 determine single specimens upon simple descriptions. 



The details of form and livery upon which I have endeavored 

 to build the subdivisions of the arrangement of the species, are 

 of a very doubtful profit, because of the difficulty of defining 

 them clearly, so that they must not be absolutely relied upon. 



A. Form rather stouter, abdomen rather wide in the middle, but 

 yet attenuated before. The fossette of the posterior face of 

 metathorax rounded, always distinct. (Fossette of meta- 

 thorax sometimes margined superiorly.) 



a. Thorax but slightly adorned with yellow; {sometimes quite black, with a 

 yellow spot under the wing) ; post-scutel quite black or adorned with two 

 yelloio dots. 1 



13*2. O. IVortoniantlS Sauss. — Niger ; clypeo antice anguste pro- 

 dncto, subbidentato ; metanoto rugoso, foveola striata, marginibus 

 punctatis, obtusis ; abdomine ovato, prirao segmento valde punctato, 

 cupuliformi,basi subtruncato, sessili, secundo magis tenuiter punctato; 

 puncto mandibulari, frontali, post-oculari, lineola in ociilorum sinu, 

 macula subalari, punctis 2 post-scntelli et abdominis, segmentorum 1', 

 2 1 margine tenuiter, flavis ; 2° segmento utrinque flavo-punctato et 

 partiin ilavo-inarginato ; genibus et tarsis ferrugineis ; tibiis anticis 

 flavis. 9 • 



Var. a. Thorace omnino nigro, macula flava subalari. — b. Secundo abd. 

 segmento baud flavo-marginato. 



Odyn. Nortonianus Sauss. Rev. de Zool. XXII, 1870, 105, 28, $>. 



Total length, 9 mm. ; wings, 7 mm. 



9 . Rather small. Clypeus somewhat triangular, rather narrowly 

 produced and subbidentate. Prothorax somewhat angulated. 

 Post-scutel short, forming on its anterior (or superior) part a 

 rounded transverse carina, with a little insensible medial tubercle; 

 its hinder face slightly convex. Metathorax rugose, punctured, 

 quite rounded, its concavity strigose, not marginate. Head and 

 thorax not very coarsely cribrose. Abdomen cylindrical, ovoid ; 

 the first segment short, truncate, and rounded anteriorly, as 

 cribrose as the thorax, the 2d slightly constricted at base, more 

 finely punctured, becoming more coarsely punctured on its hinder 

 part 



Comp. also A. Peyroti, var. 



