288 COLEOPTERA OF NORTH AMERICA. 



what rough in D. geminatus ; hind femora less deeply silicate 

 beneath, and with several short elevated ridges on the inner sur- 

 face in Orthosoma. In both genera the narrow epipleural por- 

 tion of the elytra is transversely striate, forming a stridulating 

 organ upon which the ridges or edges of the hind femora grate 

 to produce a sound. 



Among our three species I recognize but two genera, Dero- 

 brachus and Orthosoma, distinguished sufficiently by the cha- 

 racters above given. Braderochus Bnquet, to winch D. gemi- 

 natus Lee. has been referred, does not seem to me sufficiently 

 distinct. Besides the sexual characters above mentioned, the 

 5th segment in the % of Derobrachus is broadly emarginate, the 

 6th visible and also emarginate; and the last dorsal is truncate 

 and emarginate ; the 5th ventral is elongate and truncate in the 

 9, but the 6th is not visible. 



In Orthosoma the 5th ventral is rounded in the 9, but broadly 

 truncate in the £, leaving the 6th visible. 



The distribution of the species is as follows : — 



Derobrachus brevicollis, Southern States. 



D. geminatus from Texas, through Arizona to Lower California. 



Orthosoma brunneum Forst. (cylindricum Fabr.), is generally 

 distributed over the Atlantic States. 



Tribe IV.— PRIOIVINI. 



In this tribe the mandibles are moderate in size, acute, and 

 similar in both sexes. The eyes are coarsely granulated, usually 

 large, transverse, convex, and approximated. The antenna? have 

 from 12-21 joints, varying according to species, the joints are 

 conical and imbricated, much heavier in the % than the 9, the 

 poriferous system commences on the 3d joint, and covers nearly 

 the whole surface of the 4th and following joints. In Prionus 

 % and 9 the sensitive surface is reticulate, with fine elevated 

 lines, hut in ITomresthesis %, the surface is quite uniform. The 

 sides of the prothorax are armed with 3 acute teeth in Prionus, 

 but in Homeesthesis Integra and emarginata the apical and basal 

 teeth are obsolete, so that the sides become unidentate. 



P. paljwis Say, has the form of Prionus, but the antennae 

 are as in Homa3sthesis. 



The narrow epipleural margin is striate transversely, and stri- 

 dulation is produced by rubbing against this surface the sharp 



