loo Field Museum or Natural History — Zoology, Vol. X. 



Measurements. Type: Total length 201; head and body 116; 

 tail 85; hind foot 24. Skull: Zygomatic breadth 13.8; breadth of 

 braincase 13; interorbital breadth 5.5; nasals 10.6 x 3.4; palatine foram- 

 ina 5.7; diastema 7; upper molar series 4.6. 



Remarks. This form is readily distinguished by its wholly black 

 tail and feet, the other forms of A. mollis having grayish feet and a 

 bi colored tail. These characters are seen in their incipiency in speci- 

 mens from localities immediately west of Poco Tambo and evidence of 

 the gradation from one form to the other is practically complete. At 

 Poco Tambo the conditions are those of typical montagna with dense 

 himiid forests, but relatively cool climate. 



