BATRISINI 241 



Structurally the species have a common habitus. The truncated cordate 

 pronotum, lacking sulci, and provided with a pair of large conspicuous ante- 

 basal spines is typical of the genus. In addition some species have a pair of 

 smaller spines, one on each lateral margin of the pronotum between the middle 

 and apical third. The body is usually large, always elongate-cylindrical. In com- 

 mon with the arthmioid genera, the abdominal margin of the first tergite is 

 strongly formed by both an external and an oblique internal carina, and the 

 following tergites have the "margin" formed by a very short basal external 

 carina on each side. The elytra are simple with a single large basal fovea and 

 sutural stria on each elytron in the majority of the species, while in a new 

 subgenus there are no basal foveae. 



The males have the antennae, metasternum, and intermediate legs abnor- 

 mally modified in most of the species; where both sexes are known the females 

 have relatively unmodified antennae, metasternum and intermediate legs. 



Oxarthrius was considered a subgenus of Batrisus until 1904. The genus is 

 more allied to Iteticus than to other neotropical aggregates, from which it is 

 distinct in lacking any dorsal elytral stria and the possession of antebasal 

 pronotal spines. 



The following arrangement of the genus is necessitated by the accumulation 

 of novel data: 



Key to Subgenera {both sexes) 



Each elytron with a single basal fovea; distal segment of maxillary 



palpi with simple, unscarred external face 



SUBGENUS OXARTHRIUS, s.s. 



Elytra without basal foveae; distal segment of maxillary palpi with a 



distinctive scar on the external face near middle 



SUBGENUS BAROXARTHRIUS, new subgenus 



Subgenus Oxarthrius, s.s. 



Key to Species {both sexes) 

 (Modified from Rafifray, 1897) 

 The following key is complete with the exception of Oxarthrius attaphilus 

 Bruch. 



Pronotum, in addition to the large antebasal spines, with a small spine 



or tooth on each lateral margin between middle and apex 2 



Pronotum with lateral margins not armed 7 



2. Pronotum conspicuously rugose and granular 3 



Pronotum nearly glabrous, at least shining and lightly punctulate ... 5 



3. Antebasal spines of pronotum long, compressed, sharp-pointed; lateral 



spines relatively large; 1.76 mm rugosicollis Male 



Antebasal spines of pronotum relatively shorter, less pointed, and di- 

 rected posteriorly; lateral spines relatively small; 2.8 mm 4 



4. Intermediate femur with a small pubescent tubercle near base ; inter- 



mediate tibia with an apical spur rugosus Male 



