254 Bulletin American Museum of Natural History. [Vol. XVI, 



into two distinct groups, through well-marked differences of 

 size, coloration, and cranial characters, namely, the D. 

 marsupialis group and the D. 'azarce' or paraguayensis group. 

 The first ranges from Panama southward, extending down 

 the Pacific coast as far, at least, as northern Peru, and 

 also across northern South America from western Colombia 

 to Trinidad, and southward east of the Andes, to Bolivia, 

 northern Argentina, Uruguay, and southern Brazil. It is 

 not, however, the same throughout this vast range, but is 

 separable into a number of well-marked forms, the extremes 

 of which, while widely diverse, are connected by intergrada- 

 tion. The smallest forms of this group are considerably 

 larger than the largest forms of the paraguayensis group. 

 The coloration is also notably different, the marsupialis group 

 having wholly black ears x and very indistinct head markings , 

 while in the paraguayensis group the ears are either wholly or 

 in large part flesh-colored, and the black head markings are 

 generally very sharply defined on a white ground. In the 

 latter the skull is relatively shorter and less attenuated, the 

 4th premolar in both jaws is relatively much larger and 

 thicker or more peg-shaped, and the superior border of the 

 zygoma is formed posteriorly by the squamosal instead of in 

 part by the posterior extension of the malar. This character 

 alone is so constant and well marked as to readily differen- 

 tiate the skulls of the two forms. 



The paraguayensis group is found from the Rio de la 

 Plata northward to central Minas Geraes, Matto Grosso, and 

 western Bolivia, and thence northward in the Andean region 

 through Peru and Ecuador, reaching the coast at Callao and 

 probably elsewhere in Peru, and thence ranging eastward 

 through the Eastern Cordillera in Colombia and Venezuela to 

 Merida. It appears to be absent from western and northern 

 Colombia, northern and eastern Venezuela, including the Ori- 

 noco basin, and from the whole Amazonian region east of the 

 Andean foothills, and hence from all of central and northern 



1 By 'ear* is meant, in this connection, the external ear or pinna only, exclusive of 

 the'meatus, which latter often varies individually in specimens from the same locality 

 in all the forms of the marsupialis and mes-americana (californica) groups, in which the 

 external meatus may be yellowish while the pinna is wholly black. 



