NO. 5 MAMMALS OF PANAMA — GOLDMAN 49 



only in size, as a glance at the wide mouth, numerous teeth, and 

 characteristically opossum feet show. The skull of Marmosa is 

 similar to that of Philander in the permanent separation of the 

 temporal ridges, but it differs in other important respects, especially 

 the absence of distinct postorbital processes, the straight and 

 anteriorly much converged maxillary toothrows, and in the relative 

 size of the first and third upper molars. In Marmosa the third upper 

 molar is larger than the first, while in Philander the reverse is usually 

 true. For many years a single form was supposed to range north- 

 ward from South America to southern Mexico, but several distinct 

 species are now known to inhabit Middle America. 



MARMOSA MEXICANA ISTHMICA Goldman 



Isthmian Marmosa 



[Plate 21, figs. 3, 3a] 



Marmosa isthtnica Goldman, Smiths. Misc. Coll., Vol. 56, No. 36, p. i, 

 February 19, 1912. Type from Rio Indio, near Gatun, Canal Zone, 

 Panama. 



The isthmian marmosa is about the size of a large rat. It closely 

 resembles M. mitis Bangs, of the Santa Marta region of Colombia, 

 in color, but differs from that animal in larger size, relatively larger 

 braincase, broader interorbital space and actually smaller audital 

 processes of alisphenoids. The general color of the upperparts is 

 brownish cinnamon (about sayal brown of Ridgway, 1912), lighter 

 on the middle of the face, and becoming dull ochraceous buff on the 

 sides of the neck and flanks ; the underparts are between pinkish 

 buff and cream buff. It is probably a common species throughout 

 Panama. The type was trapped in an old banana plantation only a 

 few feet above sea level near Gatun. At Cana, where the opossums 

 are fairly abundant, a number of specimens were caught in banana- 

 baited traps set on hanging bunches of the ripening fruit in a planta- 

 tion. The bunches of fruit were visited by the opossums nearly 

 every night. Other specimens were taken in dense undergrowth on 

 the ground in old clearings. 



Under the name Didelphys miirina, Alston (1879, p. 200) notes a 

 small opossum which may have been this form collected by Arce in 

 Veragua. A specimen of this subspecies was recorded by Bangs 

 (1902, p. 19) as Marmosa mexicana from Boquete, Chiriqui. More 

 recently a large series, in the aggregate, of this opossum has been 

 recorded by Anthony (1916, p. 363) from Real de Santa Maria, 

 Gatun, Maxon Ranch (Rio Trinidad), Tapalisa and Tacarcuna. All 

 of these localities are in the eastern half of Panama, ranging from 



