192 Mr. O. Thomas on 
type, but that is a very old specimen. Their bulle are all 
smaller than in the type of G. cachinus, and about the same 
as in G. lockwoodi. 
11. Akodon simulator, Thos. 
6. 545, 550, 551, 555, 557, 560, 568, 570, 571, 574, 576, 
593, 596, 603, 605, 608 ; 9. 552, 558, 559, 569, 579, 581, 
588, 590, 591, 594, G09. Jujuy. 1258 m. 
d. 620, 632, 650, 658, 660, 662; ¢. 612,641. Villa 
Carolina. 500 m. 
This fine series, of all ages, shows, firstly, that A. semu- 
lator is much more hypsodont than ordinary Akodons of the 
arenicola group, being, in fact, intermediate between the 
latter and the extremely hypsodont Hypsimys. And the 
same is no doubt the case with the other large Akodons of 
the present group, most of which are known only by more 
insufficient material, often with greatly worn teeth. Degrees 
of hypsodontism are always very difficult to judge without 
specimens of many different ages; so that this series is of 
special value. 
Secondly, [ would note that A. simulator proves to be more 
variable in colour than usual, some specimens being, like the 
original set, grey anteriorly and buffy posteriorly, others with 
the buffy covering the whole body, and others, again, nearly 
uniformly brown. These differences are not local, and no 
corresponding differences can be found in the skulls. 
. Akodon sp. (near A. dolores). 
(Villa ene ) 
A skin (no. 656) from Villa Carolina, which appears to be 
quite indistinguishable from //esperomys venustus, has assigned 
to it, but L feel sure wrongly, a skull showing a very close 
resemblance to that of the Cordova Akodon dolores, an animal 
with no external similarity to the Hesperomys, and belonging 
to yet another group of Akodon. No skin in the collection 
seems suitable for this skull, which must remain undetermined 
until further collections are made. A, dolores is not specially 
hypsodont, as are A. stmulator and cenosus, nor are the in- 
cisors proodont, as is the case with A. cine and orbus, from 
Leon, Jujuy, and Otro Cerro, Catamarea, respectively. 
13. Akodon cenosus, Thos. 
¢:. 080,080, 989, 592, 595, 606; 9. 565, 566, 838, 
Jujuy. 1 ; 
