the Serro do Mar of Parand. Gl 



species or to the true arenicoJa. There is a good deal of 

 variation in its dimensions, and it is not always easy to 

 determine immature specimens. 



As the species is common over a large part of the longest 

 explored region of IJrazil, it may easily prove to have had 

 some earlier name than CMr.sor applied to it ; but in the mean- 

 while I use that which seems most certainly pertinent. 



In my previous paper, under the heading oi likodon sp., I 

 inferred that Wagner's Ilesperomys hrachyurus was a member 

 of that genus ; but further consideration convinces me that, 

 like Lund's Mas lasiurus (to which it is closely allied), it is a 

 Zygodontvmys, and has nothing to do with the Akodon group. 



The Museum owes to Dr. von Ihering an example from 

 ISao Paulo, which agrees closely with what Wagner and 

 Ntitterer say of //. brachyurus, especially in regard to the 

 hairiness of the tail and the subequality of the first and fifth 

 posterior digits. 



9. Akodon serrensisj sp. n. 



5 S ' August and September, 1901. 



Sizemediuni, lar<;er than A.arenicola,s,mA\\ex i\x-An A .cursor . 

 Fur thick and woolly, of average length; hairs of back about 

 8-9 millim. long. General colour above uniform finely 

 grizzled olivaceous, nearest toRidgway's " bistre," this colour 

 being obtained by a tine mixture of blackish and yellowish. 

 Sides scarcely lighter than back. Under surface ochraceous, 

 dulled by the slaty bases of the hairs showing through ; line 

 of demarcation on sides not sharply marked ; anal region 

 ))rominently rich unmixed ochraceous. Head like liodv, tiie 

 cheeks rather more ochraceous. Ears dark brown, rather, 

 but not conspicuously, darker tiian the body. Limbs like 

 body ; hands and feet dull brown above. Tail rather longer 

 than the body without the head, very finely ringed, almost 

 naked; the minute hairs brown above, dull white below. 



Skull, as compare! with that of A. arenicola, larger, with a 

 longer and narrower muzzle, much broader interorbital rei^ion, 

 shorter palatal foramina, which only reach backward to the 

 anterior third of ?»', and broader choanae. Molars very larg.i 

 in proportion, as large as those of the much bigger species 

 A. cursor. 



Dimensions of the type (measured bv Mr. Robert in the 

 flesh) :— 



Head and body 88 millim.; tail 78; hind foot, s. u. 22 

 c. u. 2-i ; ear 18. 



Skull: greatest length 27; basilar length 21; greatest 



