44 Mr. H. W. Bates on 



(^ . Antennae longitudine corporis^ articulis basalibus 

 tribus aspere punctatis_, omnibus intus denticulatis ; 

 tarsi omnes lati_, lobis rotundatis. 



9 . Antennge dimidium corporis attingentes, tenui- 

 ter punctatae, nee denticulatae ; tarsi lobis com- 

 pressis. 



The thorax is coarsely scabrous on the sides in both 

 sexes, and has a broad shining space in the middle, 

 finely punctured ; the basal joint of the antennge is 

 shorter and thicker than in any other known species. 

 The female has not before'been described. 



The species occurred at Santarem, Obydos and Manaos, 

 on the Amazons. 



3. Ctenoscelis Nausithous. 



Buquet, Ann. Soc. Bnt. Fr. 1843, p. 236, pi. 9, 



f. 2, S. 



Ct. gracilior, thorace angustior; piceo-niger, thorace 

 scabroso, spatio mediano Isevi subtiliter punctato ; 

 elytris apice rotundatis, angulis suturalibus dentatis. 



Long. 3 unc. 4 lin. 



(J . Antennae corpore longiores, articulis extus 

 breviter tuberculatis, tribus basalibus subtiliter punc- 

 tatis, reliquis Igevibus. 



$ . Antennae dimidium corporis superantes, spar- 

 sim punctatse; tarsi lati, lobis posticis acutis. 



The shape of this species is much more slender than 

 in the rest of the genus ; the thorax of the female is 

 scarcely to be distinguished from that of the same sex in 

 Ct. Dyri'hacns, but the elytra differ in being much nar- 

 rower, and especially more parallel- sided ; the tibiee also 

 are relatively longer, and more slender. 



I met with one example only of this species, a female, 

 at Serpa, near the mouth of the River Madeira. Not 

 being acquainted with the male, I have drawn up the above 

 imperfect diagnosis from the description of M. Buquet, 

 who obtained the insect from Bolivia. 



Lacordaire founds his generic characters of Ctenoscelis, 

 in great measure, on the sexual differences in the punc- 

 tuation of the thorax, as shown in Ct. ater and acantho- 

 ptis J this part of his diagnosis will no longer be appli- 

 cable, as Ct. Dyrrhaciis and Nausithous show no such 

 differences. 



