1904-] Allen, Mammals from Tropical America. 57 



specimens agrees with what I take to be true derbianus, repre- 

 sented by four specimens from the Rio Cauqueta, in the 

 Cauca region of Colombia, which have the greater part of the 

 dorsal aspect of the body, and also the limbs, intense light 

 rufous, with a broad, very sharply defined gray shoulder-stripe. 



While I provisionally refer the Chiriqui and Costa Rica 

 specimens to pallidus, they certainly show that the form is 

 subject to a wide range of individual variation in color, and 

 that the supposed light color and absence of a gray shoulder- 

 stripe fail as distinctive characters of this form. 



The Chiriqui specimens are all old adults, as shown by the 

 skull. The external measurements, taken from the collector's 

 labels, are as follows: 3 males, total length, 763 (730-800); 

 head and body, 300 (270-320); tail vertebrae, 463 (450-480); 

 hind foot (without claws), 43 (40-45); ear (from notch), 41 

 (38-45). Three females: Total length, 740 (725-765); 

 head and body, 285 (280-290); tail vertebrae, 458 (435-480); 

 hind foot, 43 (40-44); ear, 39 (38-40). 



The largest male skull measures 64 x 36, the average of the 

 males being about 61 x 35, or the same as the type of pallidus. 

 The external measurements, however, are greater, particu- 

 larly the length of the tail, than those given by Mr. Thomas 

 for the type. I 



There is much less sexual difference in size than occurs in the 

 Didelphis group. 



3. Metachirus fuscogriseus Allen. Six specimens : Boque- 

 ron, 5, Oct. 30 and 31, and Nov. 30; locality not given, i. 

 This latter is a small, very pale female, in worn pelage. 



Two very old males (Nos. 18904 and 18907) measure as 

 follows: Total length, 640, 640; head and body, 350, 310; 

 tail vertebrae, 290, 330; hind foot, 47.5, 50; ear, 37.5, 35. 

 Two very old females (Nos. 18903, 18906): 610,540; 310,280; 

 300, 260; 45, 50; 40, 31. The two old male skulls measure, re- 

 spectively: Total length, 80, 75 ; zygomatic breadth, 41.5,41.5; 

 an old female skull, 78 x 40. The sagittal and occipital crests 

 are greatly developed and the teeth are much worn in all three. 



1 Mr. Thomas gives the total length of the type as 587 mm., obviously an error for 

 687. 



