228 GEO. H. HORN, M. D. 



versely oval," and resembles the orbiculate form but is shorter and 

 the sides at middle are either straight or slightly sinuate, the anterior 

 sinuous impression is usually deep and the disc of the thorax less 

 convex. The last named species is peculiar in having the thorax 

 densely clothed with yellow silken pubescence. 



The elytra present but little that is peculiar except that mentioned 

 above. The sculpture is very little variable but the color very much 

 so in several species. The elytra have at the sides a marginal line 

 very distinct in all the species except carolinus. The part below this 

 line is called in the subsequent pages the "epipleural fold," and is 

 spoken of by most authors as the epipleurou but such is not the case, 

 the epipleurse being extremely narrow pieces along the extreme edge 

 of the elytra. The marginal line varies in length in the species, in 

 some reaching from the outer apical angle nearly to the humeral 

 umbone, in others but half that length. The epipleural fold is 

 narrow in carolinus, wide in the other species. 



The tibiss vary also, the posterior pair being distinctly arcuate in 

 carolinus, marginatus, ohscurus, orhicollis, americanus and Saj/i, while 

 the last two have the middle tibiae also curved. There has always 

 seemed to be great trouble in properly defining the limits of species, 

 and the numerous synonyms show how far separation has been pushed 

 on a color basis alone. Those which have no other claim to separation 

 their differences of color have been rejected and structural characters 

 taken as the basis of separation. Two species acknowledged in the 

 following pages are still doubtful in my mind but they are retained as 

 distinct for reasons given. 



The following are the species recognized in the subsequent pages : 



Group 1. — Thorax oboval, extremely narrowly margined, disc very unequally 



punctured, without anterior sinuous line carolinus Linn. 



Group 2. — Thorax orbicular, sides and base with wide flattened margin, disc 

 equally punctulate, sinuous line usually distinct. 

 Elytra without erect hairs, disc of thorax red. 



Middle and posterior tibiae arcuate amcrjeanns Oliv. 



Elytra with erect hairs, disc of thorax black. 



Middle and posterior tibiae arcuate Sayi Lap. 



Tibiae not arcuate orbicollis Say. 



Group 3. — Thorax transversely cordate, sides narrowly margined and sinuate 

 at middle, anterior sinuous line distinct. 

 Posterior tibise arcuate. Disc of thorax nearly smooth. 



First joint of club red inarginatus Fab. 



First joint of club piceous .obscuriis Kby. 



Posterior tibiae straight. Disc of thorax punctate. 



Antennal club and colorof elytra very variable. ..guttnla Motsch. 



