NO. 5 MAMMALS OF PANAMA — GOLDMAN 87 



Subgenus MEGADONTOMYS Merriam 

 PEROMYSCUS FLAVIDUS Bangs 



Volcan Mouse 



Megadontomys Havidus Bangs, Bull. Mus. Comp. Zool., Vol. 39, No. 2, text 

 figs. 5-7, p. 27, April, 1902. Type from Boquete, Volcan de Chiriqui, 

 Panama (altitude 4,000 feet). 



Peroniyscus flavidus is a large member of the subgenus Megadon- 

 tomys, allied to P. plrrensis, but paler, more ochraceous in color, with 

 a shorter hind foot. It differs also in cranial and dental details, 

 especially the tendency to division exhibited by the anterior lobe of 

 the first upper molar. 



This species was discovered by W. W. Brown, Jr., in the course 

 of his work for Outram Bangs on the Volcan de Chiriqui. He found 

 it common in the upland forest at from 3,000 to 5,000 feet altitude, 

 but no specimens were taken above or below these elevations. The 

 species thus seems to be restricted to about the same altitudinal range 

 as P. pirrensis and the two are apparently isolated by low-lying areas 

 unsuited for their habitation. 



Specimens examined: Boquete, 32' (including t>'pe). 



PEROMYSCUS PIRRENSIS Goldman 



!Mount Pirrc Mouse 



[Plate 23, figs. 5, 5a] 



Peromyscus pirrensis Goldman, Smiths. Misc. Coll., Vol. 60, No. 2, p. 5, 

 September 20, 1912. Type from near head of Rio Limon, Mount Pirre, 

 eastern Panama (altitude 4,500 feet). 



The Mount Pirre mouse is a large member of the subgenus 

 Megadontomys. It is similar to P. flavidus of the Volcan de Chiriqui 

 but is decidedly darker, less ochraceous in color, and has a longer 

 hind foot ; the skull is larger, with longer, slenderer rostrum ; the 

 anterior lobe of the first upper molar is very narrow and in some 

 examples entire, in others slightly notched. 



While evidently more closely allied to P. flavidus than to any other 

 known form, P. pirrensis dift'ers from that species notably in denti- 

 tion. The anterior lobe of the first upper molar is narrower, less 

 extended internally, and the longitudinal notch is faint or absent. 

 The supplementary cusps are rather weakly developed for a Mega- 

 dontomys, and the general form of the tooth suggests the 5-tubercu- 

 late condition of typical Peromyscus. In P. flavidus, on the contrary, 

 the division of the anterior lobe being more complete the cusp 



*Twent}'-five in collection Mus. Comp. Zool.; five in Amer. Mus. Nat. Hist. 



