I 74 Bulletin American Museum of Natural History. [Vol. XIV, 



Huehuetan, 7 3 black, 4 gray, and 3 additional skulls ; Tuxtla, 5 r black 

 and 4 gray. 



Guatemala (near Chiapas border) : Jacaltenango, 3, black ; Nenton, i, 

 gray; Escondido River, i, very young ; "Guatemala," without special locality, 

 4 3 gray, i black. 



Total, 46 and 5 additional skulls. 



Didelphis marsupialis tabascensis is a very strongly marked form, 

 ranging, so far as present material shows, from the vicinity of 

 Vera Cruz to Frontera, Tabasco, and across the State of Chiapas 

 to northern Guatemala. The character of the long nasals, 

 terminating posteriorly in a V-shaped angle, runs throughout 

 the series with a small number of exceptions, while the speci- 

 mens from the immediately adjoining localities to the northward 

 and westward, in the States of Vera Cruz and Orizaba, are almost 

 uniformly characterized by short nasals more or less truncated 

 posteriorly. The form of the nasals is thus much as in D. vir- 

 giniana and D. m. texensis, or even in D. richmondi from Nicara- 

 gua and Costa Rica. The increase in the length'of the nasals, in 

 this as in other forms with long nasals, is not due to any increase 

 in the length of the rostral portion of the skull but to the greater 

 posterior extension of the nasal bones. 



The variation in the form of the nasals in D. marsupialis and 

 its subspecies is summarized, in comparison with D. virginiana, 

 in the following tabular statement: 



RATIO OF NASALS TO THE BASAL LENGTH OF SKULL. 



