^^ [February, 



b. Antennae in frontenn insertae. 

 Scrobiculi antennales medii, laterales, prosterno subpro- 



ducto ......... Teretrius Er. 



Scrobiculi antennales ad prosterni latera siti . . . Plegaderus Er. 



Scrobiculi antennales antici Onthophilus Leach. 



Scrobiculi antennales medii, laterales, prosterno truncate Abr;eus Leach. 



HisTER Linne. 



I have included in this genus Omalodes and Platysoma; as they are founded 

 on slight differences in the form of the tibiae. Plaesius and Placodes will also 

 probably enter here ; at least I cannot find anything to separate them, except 

 differences in the spines of the posterior tibiae. 



The posterior tibiae of this genus, are generally broad, and externally armed 

 with two series of spines : sometimes a range of bristles on the posterior face of 

 the tibiae is enlarged so as to simulate a third row of spines ; sometimes (Hister 

 arcuatus Say) the whole outer surface of the tibiae is rough with confused spines ; 

 in H. costatus (n. sp.) the posterior tibiae are narrow, and the spines are very 

 fme : these tibiae are usually not toothed on the outer margin, yet in H. sexstri- 

 atus Lee. they are distinctly four-toothed : they are also toothed in the species 

 referred to Omalodes and Platysoma, the number of teeth in the latter being 

 variable, and the teeth themselves frequently indistinct: they are entirely smooth 

 in some small species allied to H. subrotundus, and belonging to Erichson's 3d 

 division ; the posterior feet are smooth, and the intermediate ones armed with a 

 single tooth near the apex in H. corticalis Lee. ; finally, the posterior tibiae are 

 broad, very much compressed and finely serrate in Omalodes Harrisii Lee. 



The anterior tibiae are broad, compressed and more or less distinctly toothed 

 on the outer margin, usually with a single row of very short articulated spines; 

 on the anterior face is a groove for the reception of the tarsus ; the inner margin 

 of this groove is sharply defined; the outer margin indistinct, in most species ; 

 more distinct in the species referred to Omalodes ; some of the species of Platy- 

 soma have the outer margin distinct, while in others (H. Carolinus Payk.) it is 

 quite indistinct. The species, with the exception of the large tropical species, 

 which would probably form a separate division, can be arranged according to 

 the following table ; the internal marginal stria of the thorax, when it exists, is 

 entire, and extends around the whole apex of the thorax ; the outer stria always 

 ends at the anterior angle. 



A. Thorax stria marginali interiore integerrima, antice ambiente. 



* Thorax stria marginali margini valde approximata. 

 Thorax stria marginali unica ; (tibiae posteriores dentatae.) Omalodes Er. 1. 

 Thorax striis marginalibus duabus ; (tibiae post valde compressae serrulatae.) 2. 



** Thorax stria marginali interiore a margine remota. 



a. Thorax margine ciliato ; (scrobiculi antennales non profundi.) 



Tibiae posteriores dilatatae ........ 3. 



Tibiae posteriores tenues. ........ 4. 



b. Thorax margine glabro ; (scrobiculi antennales profundi.) 



a. Tibiae posteriores subdentatae ....... 5. 



b. Tibiae posteriores biseriatim spinulosie. 

 f Mesosternum emarginatum. 



cL. Epipleurae excavatae unistriatae : (tibiae anticae multidentatae) . 6. 



/3. Epipleurae non excavatae, pluristriatae. 



Tibiae anticae parce dentatae, epipleurae bistriatac . . . . 7. 



Tibira anticae parce dentatae, epipleurae tristriatae . . . .8. 



Tibifjc anticae serrulatae vel muticae, epipleurae bistriatas . . .9. 



ft Mesosternum truncatum. 



Epipleurae bistriatae . 10. 



Epipleuraj angustissimac, unistriatac , . . . ; . .11. 



