Mr. Walker's Descriptions of Clialcidites. 45 



Hesperomys arviculoidcs, Pict.* H. olivaceo-brunneu?, nigro-adsper- 

 sus, eubtus pedibusque canus, Cauda dimidii corporis longitudine, 

 dense pilosa ; vellere nitido molli. — Corpus 5'' 5'", cauda 2'' 8'". 

 Brasilia. Mus. Mouac. 



Hesperomys orohiniis, Wagn. H. supra brunneo-flavus, subtillssime 

 uigro-adspersus, subtus flavido-albescens, auriculis postice nudis, 

 pedibus fuscis ; cauda corpore multum breviore, squamata, nigri- 

 cante. — Corpus 5'', cauda 3' 5'". 

 Brasilia. Mus. Monac. 



Hesperomys suhflavus, Wagn. H. supra brunnco-flavidus, subtus al- 

 bidus, pedibus sordide albidis ; cauda longitudine corporis, squa- 

 mata, raripilosa. — Corpus 6', cauda 6'. 

 Brasilia. Mus. Monac. 



Dasyprocta nigricans, Natt. D. tota e nigro alboque variegata, tergo 

 concolore. — Corpus 22". 

 From Borba on the Madairo, and from Rio Negro above Cocuv. 



VII. — Descriptions of Chalcidites discovei'ed by C. Darwin, Esq. 

 By Francis Walker, Esq., F.L.S. 



Thoracantlia Latieillii, Fem. Nigru-cyanea, antcnnce piccce, pedex fiilvi, 

 femora fusca, ales limp'ulcc. 



Thoracantlia Latreillii, Gui-riu, Icun. Rcyiw Aiiuii., Insecies, pi. G7. 



Corpus gibbura, altuin, coiiipvessum, incurvuin, coiivcxum, nigro-cya- 

 neum, nitons, glabruni : caput pavvuni, transversuni, dcclive, snbtilissime 

 striatum; vertex sat latus ; frons impressa, ad os angustior : oculi ridi, nie- 

 diocres, non extantes : ocelli 3, remoti, rufi, triangulum fingentes; niedius 

 perparum antepositus : antennae picea?, parvte, graciles, extrorsum cras- 

 siores, apice fulvas, capite vix longiores; articulus 1"* longus, sublinearis ; 

 2'" cyathiformis ; o"* et 1"' miiiinii ; o"* et sequeiites breve.s, a])pioximati ; 

 clava conica, articulo 10° diiplo longior : thorax maximus : protliorax bre- 

 vissimus; sternum parvum ; dorsum minimum, supra non conspicunm : 

 mesothoracis scutvmi transverse striatum, longitudine latins, per medium ob- 

 solete sulcatum; parapsidum suturne bene determinatie, postice approximate}; 

 scutellum transversnm, breve, snbtilissime rugulosum, per medium obsolete 

 sulcatum : uietathoracis dorsum maximum, snbtilissime rugulosum, quasi 

 bipartitum ; pars antica longitudine vix latior, per medium obsolete sulcata ; 

 pars postica longior, fissa ; fissin-a postice dehiscens, similitudine ylA'/tvV/is 

 elytrorum, abdominis apicem altingcns : petiolus vix conspicuus: abdomen 

 compressum, apice snbtilissime rugulosum, basi Itevc, thorace paullo brevins 

 etangustins; segmentum l""" dorsum et sternum onuiino obtegens : pedes 

 fulvi, graciles, simplices, subanjuales ; coxse nigro-cyanea?; trochanteres 

 picei ; femora fusca; tarsis articuli 1° ad 4""' curtantes, ,5'"* 4" paullo lon- 

 gior ; ungues et pulvilli minuti : alje limpidoa, parvce ; squamulse fulva; ; 

 nervi albidi, vix conspicui, basi fulvi ; nervus humeralis idnari niulto lon- 

 gior, radialis vix uUus, cubitalis brevissimus; stigma minimum. (Corp. 

 long. lin. 2; alar. lin. 3.) 



Brazil. 



* I have retained the name of Mus. arviculoides, Pictet, which was written 

 on the label of the specimen when purchased. 



