St (tpliijlitiidce of tJie Amazon Valley. 285 



tibiae nearly black ; the tarsi strongly infuscate. The 

 central notch of labrum shallow, but rather broad. 



The notch on the ventral plate of the 7th segment of 

 the hmd body in the male is very deep and j^arallel-sided. 

 In the female the extremity of the same plate forms a 

 large triangle, and on each side of this at the base is a 

 stout, very short tooth. 



Ega and Tapajos ; several individuals. 



This species is allied to P. cequinoctialis, Er., to judge 

 from description. I have several closely-allied South 

 American species, but fail to ascertain without doubt 

 which of them is Erichson's species. 



2. PcBderus tridens, n. sp. Angustulus, niger, clytris 

 humeris angustatis, thorace fere brevioribus, cyaneis ; 

 abdominis segraentis quatuor primis, thorace, mesosterno, 

 mandibulisque rufis ; palpis, pedum basi, antennarum basi 

 et apice testaceis, his medio fuscis ; elytris crebre fortiter 

 ruguloso-pimctatis. Long. corp. 4^ lin. 



Antennas slender, 1| lin. in length, 3 basal joints yellow, 

 the 3 apical ones reddish, the middle ones deeply infuscate. 

 Palpi yelloAV, apical joint obscurely infliscate at apex ; 

 mandibles and labrum reddish, the latter with the central 

 excision very small. Head black, with the neck reddish, 

 rather elongate, sparingly and finely punctured, the 

 punctures wanting on the middle. Thorax red, not quite 

 ^ lin. in length, and not f lin. in width, a good deal nar- 

 rowed behind ; the surface shining and almost impunctate. 

 Elytra narrow, narrower at shovilders, their greatest 

 length about that of the thorax, bluish-green ; coarsely and 

 rather deeply but iiTegularly punctured, so that the in- 

 terstices are rugulose. Four basal segments of hind body 

 red, the two apical ones blackish. ISIesostenium and 

 scutellum red. Legs long and slender, the coxre and base 

 of femora yellow ; apex of femora infuscate, the hinder 

 much more broadly so than the anterior ; tibias and tarsi 

 also infuscate. 



In the female the ventral plate of the 7th segment of 

 the hind body ends in an elongate pointed central spine 

 in the middle, and on either side in a shorter slightly 

 curved spine ; the narrow tongue-like process, which forms 

 the dorsal plate of the 8th segment, is much longer than 

 the broader ventral plate. 



Tunantins ; a single female. 



