Staj)hi/linid(B of the Amazon Vallei/. 405 



it being considerably broader than the elytra and more 

 arched transversely. As this is probably an extreme 

 sexual characteristic, my description has been made from 

 the smaller male, which, in the development of its thorax, 

 quite resembles the female. 



2. Piestus bicornis, 01., Er. 



Para; two female specimens. Var. Oxytelinus, Lap.; 

 seven specimens from Ega. I am very doubtful whether 

 this so-called variety be not rather a distinct species. 



3. Piestus spinosus, Fab., Er. 

 Para and Ega ; six individuals. 



4. Piestus frontalis, n. sp. Depressus, rufescens, 

 nitidus, antennis elongatis ; capite vertice bi-impresso, 

 fronte spinis duabus brevibus distantibus arraata; pro- 

 thorace medio canaliculato, et punctato ; elytris punctato- 

 striatis. Long. corp. 4^ lin. 



Antenna elongate and rather slender, 3g lin. in length; 

 the three basal joints red, the others pitchy. Mandibles 

 moderately long, greatly curved, each with a very long 

 transverse tooth on the inner side ; in the middle and on 

 the upper side with a tooth some distance from the 

 extremity; on the right mandible this tooth elongate and 

 spine-like. Head shining dark red, without punctures; 

 the front armed on each side with a short straight horn, 

 the distance between the two horns being about § lin. ; 

 within the antennal elevations the surface is depressed on 

 each side, the two depressions are not connected by a 

 channel. Thorax strongly transverse, f lin. in length by 

 1:^ in width; very shining red, with a channel along the 

 middle, and the disc with a few distinct punctures. Elytra 

 Jr| lin. in length by fully \^ va. width, each with five deep 

 punctured stria?, and with traces of a 6th sti'ia externally. 

 Hind body broad, infuscate-red, with the extremity paler, 

 coarsely but not closely punctured. Legs red. Hind 

 margin of prosternum in the middle almost straight; 

 mesothoracic keel very obsolete. 



Ega; a single individual, of doubtful sex. 



Obs. I. — Though closely allied to P. spinosus, this species 

 is rather smaller, and is very readily distinguished by the 

 diiferences of the mandibles, of the frontal horns, and of 

 the vertex. 



