Species o/'Rcitliiodon S^c.from Argentina. 475 



Dimensions ot" the type : — 



Head and body 155 mm. ; tail lO-i ; liind foot 32 ; 

 ear 27. 



ISkull : trroatest length 37 5 ; condylo-incisive length 35 ; 

 zygomatic breadth 21 ; upper molar series 7*2. 



Hab. Mar del Plata, on the south-eastern sea-coast of 

 Buenos Ayres Province. 



Tijpe. Adult f.Mnale. B.il. no. 12. 12. 11. 1. Brought 

 home alive by W. A. Smithers, Esq., and presented by the 

 Zoological Society. Lived about a month at the Zoological 

 Gardens. Two specimens from Mar del Plata, and another 

 from "Buenos Ayres" received in 1882 from Mr. A. W. 

 White. 



And an exactly similar colour-modification occurs on the 

 north side of the La Plata among; the more naked-soled forms. 

 Here the typical R. ti/picus from Maldonado is the dull sea- 

 coast form, and the following the inland one: — 



- Reithrodon tijpicus currentium, subsp. ti. 



General characters of R. ii/piciis, with soles similarly naked 

 to behind the ])osterior pads, but colours throughout more 

 brightly contrasted. Back mixed buffy grey, sides and belly 

 strongly washed with bnffy. Area round eyes reaching back 

 to ears and bases of proectote bnffy, terminal part of proectote 

 dark brown ; metentote bnffy. A well-marked patch on sides 

 of neck below ears brown, contrasted with the pale areas 

 round it. Hands and feet white ; tail almost white, the 

 usual darker line along its top quite inconspicuous. 



Dimensions of the type : — 



Head and body 139 mm.; tail imperfect (another specimen 

 IOJS mm.) ; hind foot 31 ; ear 'IQ. 



>^kull : gieatest length 'Mr'i ; condylo-incisive length 34 ; 

 zygO!iiatic breadth 19 ; uppt-r molar series 7"3. 



Hah. Corrieiites. Typ(; from Goya. 



T,ii>e. Adult male. B.M. no. "98. 12. 3. 4. Original 

 nnmher 9-1. Collected 23 July, 1895, by Mr. li. Perrens. 

 Presented by Oldfiold Thomas. 



The original type of Waterhouse's R. typiats^ collected at 

 ^laldonado by Darwin, is now much faded, but it evidently 

 never had the wcll-conti'astod marki;igs of the Corrientes 

 form. 



Ahrocoma ludini, sj). n. 



A drab-coloured Ahrocoma with large feet and tail and 

 shorter ears than A. cinerea. 



