from North-western Patagonia. 205 
Dimensions of the type :-— 
Head and body 87 mm.; tail 79; hind foot 22 ; ear 15. 
Skull: greatest length 25°7; condylo-incisive length 23 ; 
zygomatic breadth 12°6; nasals 9°8 ; interorbital breadth 4-1 ; 
breadth of brain-case 12; palatilar length 10; palatal fora- 
mina 6 ; post-foraminal palate 3°2 ; upper molar series 3°7, 
Hab, as above. 
Type. Young adult male. B.M.no.19.1.1.34. Original 
number 108. Collected 26th February, 1918. 
This appears to be the most southern of the widely spread 
olivaceus-arenicola group, which ranges from here northwards 
to Keuador, and the members of which are the most common 
field-mice in almost every locality, taking the place in nature 
of our common voles. The other species obtained by 
Sr. Budin are of the more southern wanthorhinus-canescens 
group, distinguished among other things by the mach shorter 
tail. 
[ Akodon tniscatus, sp. n. 
Size and proportions as in A, wanthorhinus, but skull more 
bowed and thickly built, with shorter muzzle. First molar 
with a deep and distinct anterior notch, which only wears off 
in old age. A white patch on the chin. 
Colour of typical race coarsely lined brown, near Ridgway’s 
“buffy brown.” 
Dimensions of the type :— 
Head and body 92 mm.; tail 53 ; hind foot 19; ear 11. 
Skull: greatest length 23:7; condylo-incisive length 21°7; 
zygomatic breadth 12-4 ; interorbital breadth 4; breadth of 
brain-case 11 ; palatal foramina 5:4; upper molar series 3°5. 
Hab. Southern Buenos Ayres Province southwards into 
Patagonia. ‘l'ype from the Valle de Lago Blanco, Koslowsky 
_region, Patagonia, 46° 8. Other specimens from Peru Station, 
N.W. of Bahia Blanea, Chubut, and Port Desire, besides the 
Budin examples referred to below. 
Type. Adult female. B.M. no. 3. 7.9.64. Original 
number XXX. Collected 26th April, 1900, by J. Koslowsky. 
Ten specimens examined, 
Our knowledge of the small Akodons of Patagonia has. 
been in a very confused condition, though an improvement 
was made by Dr. Allen, who corrected certain mistakes. that 
had been made in the labelling of the Darwin specimens, on 
which their nomenclature hangs. He rightly fixed on 
B.M. no, 55. 12, 24. 157 as the primary type of A. canescens, 
Waterh., and 55, 12. 24. 156 of A. xanthorhinus, Waterh., 
