NO. 2 NEW MAMMALS FROM EASTERN PANAMA GOLDMAN 5 



Skull. — Closely resembling that of isthmius, but rostrum slenderer 

 and premaxillse narrower posteriorly than in the type : interpterygoid 

 fossa broad, and interparietal convex anteriorly as in isthmius. 



Measurements. — Type: Total length, 260 mm. : tail vertebrae, 1 13 : 

 hind foot, 38. Average of two adult topotypes: 239 (236-243) 

 no (no-no); 36 (35-37). Skull (type): Greatest length, 38.2; 

 condylobasal length, 33-5 '< zygomatic breadth. 22.5; nasals. 10.7; 

 interorbital breadth, 13.4; palatal length, 170: maxillary toi th 1 



6.5. 



Remarks. — This pigmy squirrel is allied to the darker, richer 

 colored M. isthmius, which is based on specimens from the Truando 

 River, Colombia, and it requires no close comparison with venustulus 

 which occurs at 1,500 feet lower elevation on the same mountain 

 slope. It is readily distinguished from ■venustulus by much paler, 

 more coarsely grizzled color of upper parts. Comparing the skull 

 with that of venustulus, the interpterygoid fossa and basioccipital 

 are broader, the maxillae encroach further on the frontals between 

 the lachrymals and premaxillae, and the interparietal is subtriangular 

 instead of rectangular. The occurrence of these widely differing 

 pigmy squirrels in close proximity on the slope of the Pirri range of 

 mountains seems to show that the forms typified by aifari and 

 isthmius belong to two very distinct groups. 



Specimens examined. — Three, from the type locality. 



PEROMYSCUS PIRRENSIS, sp. nov. 



Type from near head of Rio Limon. (altitude 4,500 feet), Mount 

 Pirri, eastern Panama. No. 178997, male adult. U. S. National 

 Museum (Biological Survey Collection), collected by E. A. Gold- 

 man, May 3, 1912. Original number 2i6y?. 



General characters. — A large species of the subgenus Megadon- 

 tomys; similar to Havidus, but hind foot longer; color decidedly 

 darker, less ochraceous ; skull larger, with longer, slenderer rostrum ; 

 anterior lobe of first upper molar very narrow and entire, or slightly 

 notched. 



Color. — General color of upper parts varying from dark brownish 

 cinnamon to cinnamon rufous lined with black, becoming grayish 

 brown on head and more rusty on rump ; sides brighter, more rufes- 

 cent ; under parts dull buffy white, the plumbeous basal color of fur 

 showing through everywhere ; nose and upper sides of forearms to 

 near base of toes dusky ; toes of fore feet whitish ; hind feet whitish 

 more or less clouded with dusky over proximal half of metatarsus : 



