BY ROWLAND E. TUKNEK. 229 



Genus R H y t i d o g a s t e r, n.g. 



^. Very near Rhagigastey\ from which it may be distinguished 

 by the absence of the well defined frontal carina between the 

 eyes and by the absence of the long A-shaped carina on the 

 clj^peus. Hypopygiura without lateral spines. 



9. Head without lateral sulcse, mandibles never bidentate, 

 maxillary palpi imperfect, four-jointed. Pygidium simple. 

 Tarsal ungues simple, not bifid. Abdomen usualh^ cylindrical. 

 Corresponds to Saussure's Rhagigaster Sections B and C. The 

 difference between the females and those of the true Eliagigaster 

 seems sufticient to justify their separation, though the malt^s are 

 very near. 



Type Rhagigaster aculeatus Sauss. 



Key to the Species of Rhytidou aster. 

 cJ J', i. Median segment rounded. 

 A. Prothorax produced at the anterior angles. 



ft. Wholly black, Clypeus without a prominent tubercle, 

 a^, Epipygium rounded at apex, 

 a^. Apical margins of epipygium reflexed. R. alexins, n.sp. 



b'^. Apical margins of epipygium not retlexed. R. trisfis Sm. 



//-. Epipygium truncate at the apex. 

 a^. Epipygium very narrowly truncate, with a spine on 



each side near the base. i?. denticulatus, n.sp. 



6^. Epipygium more broadly truncate, without lateral 



spines. i?. bidens Sauss. 



h. Clypeus with an acute prominent tubercle near base. 

 a'^. Wholly black. R. cornntns, n.sp. 



c. 'I'wo apical abdominal segments red. 



a-. Clypeus with a smooth subtriangular space at the apex 



enclosed by a carina. R. iracuudus, n.sp. 



//•^. Clypeus with a triangular oblique truncation at the apex. 



a=^. Tibige and tarsi ferruginous-red. R. com2jaratus Sm. 



b^. Legs entirely black. R. tumidus, n.sp. 



d. Mesopleurps red. R. pugionatm Sauss. 

 f'.. Abdomen ferruginous, sometimes marked with black on the 



disc of the segments. R. aculeatus Sauss. 



ii. Median segment obliquely truncate. 



A. Prothorax produced at the anterior angles. 

 a. Prothorax strongly emarginate anteriorly, 

 a'-. Wholly black. R. consangaineus, n.sp. 



