Mr. Walker^s Descriptions of Chalcidites. 45 



Hesperomys arviculoides, Pict * H, olivaceo-brunneus, nigro-adsper- 

 sus, subtus pedibusque canus, cauda dimidii corporis longitudine, 

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

 Brasilia. Mus. Monac. 



Hesperomys orohinus, Wagn. H. supra brunneo-flavus, subtilissime 

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

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

 cante. — Corpus b", cauda 3" 5'". 

 Brasilia. Mus. Monac. 



Hesperomys subfiavus, Wagn. H. supra brunneo-flavidus, subtus al- 

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

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

 Brasilia. Mus. Monac. 



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

 concolore. — Corpus 22". 

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



VII. — Descriptions of Chalcidites discovered by C. Darwin, Esq. 

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



Thoracantha Latreillii, Fem. Nigru-eyanea, antenncE picea, pedes fulvij 

 femora fusca, ales UmpidcB. 



Thoracantha Latreillii, Guerin, Icon. Regne Anhn., Insectes, pi. 67. 



Corpus gibbum, altum, compressum, incurvuin, convexum, nigro-cya- 

 neum, nitens, glabrum : caput parvum, transversiun, declive, subtilissime 

 striatum; vertex sat latus ; frons impressa, ad os angustior : oculi rufi, me- 

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

 perparum antepositus : antenna? picese, parvae, graciles, extrorsum cras- 

 siores, apice fulvse, capita vix longioves; articuhis 1"^ longus, sublinearis; 

 2"* cyathiformis ; 3"* et 4"* minimi ; 5"* et sequeiites breves, approximati ; 

 clava conica, articulo 10° duplo longior : thorax maximus : prothorax bre- 

 vissimns ; sternum pavvuni ; dorsum minimum, supra non conspicuum : 

 mesothoracis scutum transverse striatum, longitudine latius, per medium ob- 

 solete sulcatum; parapsidum suturse bene determinatag, postice approximates; 

 scutellum transversum, breve, subtilissime rugulosum, per medium obsolete 

 sulcatum : metathoracis dorsum maximum, subtilissime rugulosum, quasi 

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

 pars postica longior, fissa ; fissura postice dehiscens, similitudine Melvidis 

 elytrorum, abdominis apicem attingens : petiolus vix conspicuus : abdomen 

 compressum, apice subtilissime rugulosum, basi Iseve, thorace paullo brevius 

 etangustius; segmentum 1""' dorsum et sternum omnino obtegens : pedes 

 fulvi, graciles, simpHces, subsequales; coxae nigro-cyaneas ; trochanteres 

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

 gior ; ungues et pulvilli minuti : aloe limpidae, parvse ; squamulse fulvse ; 

 nervi albidi, vix conspicui, basi fulvi ; nervus humeralis ulnari multo lon- 

 gior, radialis vix ullus, 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. 



