1873.] 281 [Horn 



Owing to the difference which have resulted, by the adoption of the 

 above method of subdivision, the system of numbering the groups has 

 not been adopted, and in lieu thereof a typical and usually a common 

 species has been selected as the representative of each group, in order 

 that the groups here made might not be confounded with those of Mar- 

 seul and Dr. Leconte. 



Group Arcuatus. 



Species of robust form. Thorax with entire margin ciliate. An.tennal 

 cavities shallow. Anterior tibiae usually bidentate. 



The following species compose this group : 

 Thorax with apical intermediate confused stria. 



Elytra with three dorsals and a sutural stria arcuatus. 



Elytra with three dorsals only sellatus. 



Thorax with two thoracic stria? only. 

 Anterior tibiae bidentate. 



Prosternal lobe acute Gloveri. 



Prosternal lobe rounded at apex. 

 Elytra with no subhumeral stria. 



Hind tibiae with outer row of spinules densely 



placed ; thorax densely fimbriate instratus. 



Hind tibiae sparsely spinulose ; thorax densely 



fimbriate biplagiatus. 



Elytra with apical subhumeral, usually deeply im- 

 pressed Ulkei. 



Anterior tibiae tridentate apical tooth divided. 



Xo subhumeral stria lucanus. 



H. arcuatus, Say. Journ. Acad. 1825, p. 34 ; Mars. Monog. 18o4, p. 

 258, pi. 7, fig. 62. 



External and internal thoracic striae entire gradually approaching at 

 base, and between them at apex a confused intermediate stria extending 

 usually beyond the middle. Three entire dorsal striae to the elytra, a 

 short basal fourth, and a sutural extending in front of middle. Sub- 

 humeral feeble at apex, humeral appendix usually deeper. Elytra black 

 with arcuate red space at middle of each. Hind tibiae with spinules con- 

 fusedly arranged. Anterior femora brownish, middle and hind femora 

 red tipped at each end with black. Length .26 inch ; 6.5 mm. 



Occurs in the Middle States, but not common. 



H. sellatus, Lee. Pacif. E. R. Eep. 1857, p. 37 ; Senevillei, Mars. Mon. 

 1857, p. 4-2-2, pi. 10, fig. 119. 



More elongate than the preceding, and with similar thoracic striation. 

 The elytra have three striae and a mere rudiment of a fourth at base, 

 the sutural is entirely obsolete. The subhumeral stria is entirely 

 wanting, with rarely but a trace represented by a few punctures, the 

 humeral appendix being entirely wanting. The hind tibiae are spinulose 

 A. p. s. — VOL. XIII. 2j 



