no SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 69 



MUS MUSCULUS MUSCULUS Linnaeus 



House Mouse 



[Mus] musculus Linn^us, Syst. Nat., Ed. 10, Vol. i, p. 62, 1758. Type 

 locality, Sweden. 



The only record I have of the occurrence of the house mouse in » 

 the republic is that of Bangs (1901, p. 644), based on a specimen 

 taken by W. W. Brown, Jr., on San Miguel Island. The species 

 probably inhabits the towns througjtiout most of the region. 



In many localities these mice take to the fields where they seem 

 to be able to exist under the same conditions, and in competition with 

 native mammals. A dark Mexican form which has apparently 

 developed differential characters has been described as subspecies 

 Mus musculus jalapcF. 



Family GEOMYIDAE. Pocket Gophers 



A single genus of this family inhabits the region under review. 

 The group, represented by other genera, reaches its greatest develop- 

 ment farther north in Middle America, but at least one outlying 

 species pushes northward into Canada. 



Genus MACROGEOMYS Merriam 

 The members of this. genus are robust burrowing animals, larger 

 than large rats. They are very unlike any of the other mammals of 

 the region and may be easily recognized by the very short ears which 

 are reduced to mere folds in the skin, the deep external cheek 

 pouches, the short, smooth, naked tail, and the large grooved upper 

 incisors. The genus is now known to range from Nicaragua to 

 extreme eastern Panama and probably enters Colombian territory. 



MACROGEOMYS DARIENSIS Goldman 



Darien Pocket Gopher ; Dueiio de Tierra ; Chuchupa 



[Plate 25, figs. 5, 5a] 



Macrogeotnys dariensis Goldman, Smiths. Misc. Coll., Vol. 60, No. 2, pp. 8-10, 

 September 20, 1912. Type from Cana, in the mountains of eastern 

 Panama (altitude 2,000 feet). 



The Darien pocket gopher is similar in general size to M. cavator 

 of western Panama, but in color is a dull brown or black instead of 

 the rich seal brown shade of the latter species. The skull is less 

 massive, more elongated, narrower posteriorly, and differs in many 

 important details; the lambdoid crest is low, nearly straight or 

 slightly convex posteriorly instead of high and sinuous ; the squa- 



M 1 



