AMERICAN COLEOPTERA. 179 



middle. In this condition it remains in sparsus. The tips of the 



elytra pass under this reflexed edge in repose and are thus 



^-_-/ ^ locked. In biarmatus and pectoralis the reflexed edge is 



ci::^ j simply notched at middle and a small acute tubercle on 



each side appears. Through the notch thus formed the 



\w/ '^ sutural dentiform process passes and the elytra are in this 



\^rp I manner firmly secured in repose. The next modification 



results in a groove running the length of the propygidium, 



limited on each side by a finely elevated line terminating posteriorly 



by joining the reflexed edge which is emarginate between them. These 



lines are exactly parallel in simplex, musculus and Vl/iei, divergent in 



front m front (I lis and sfriatus. 



The pygidium is always short and uncovered in both sexes. 



The labrum is very distinctly visible, the anterior angles 



HSHj broadly rounded and tip emarginate. In sparsus, how- 

 1^9 over, the labrum is shorter, much broader, the anterior 

 angles prominent outwardly but obtuse, the tip is more 

 deeply emarginate. 



Secondarily in importance in the accompanying table come the 

 sexual characters of the male, and from the tendency of the sexes to 

 approximate in the fcrm of their hind tibiae, a character is required 

 which will enable the male to be known even with simple tibiae. The 

 club of the male antennae is always larger, more convex, and the first 

 joint more convex on the proximal side, and more decidedly concave 

 on the distal. The club of the female is of a more decided lamellate 

 type, narrower and with the joints less enclosing, the first especially 

 being scarcely at all cupped. 



At the apical end of the posterior femora, on the lower face is a 



lamella which forms the side of the tibio-femoral 



articulation. In many of the species in the male 



this plate is developed into an unciform process, 



acute at tip. This is entirely wanting in the males 



(as I consider them), of pectoralis, simplex, Ulkei, 



sjjarsus and striatus, and exists in the others, and 



in very well developed males o^ frontalis, a small spiniform tooth occurs 



near the middle of both the anterior and posterior femora. 



The posterior tibiae % show four types. 



First — Tibiae precisely identical (?) in the sexes. I have seen 

 males only. 



Second. — Tibiae broader and more fimbriate S . 

 Third. — Tibiae obtusely dilated at middle S . 



