306 MICROTUS. 



15.5; interorbital constriction, 4.5; length of nasals, 7; palatal length, 

 13; length of upper tooth row, 7. 



D. Herpetomys. 



Third upper molar with two external and one internal closed 

 triangles and posterior crescentic loop, forming two internal salient 

 angles; first lower molar with one external and two internal closed 

 triangles, and two open triangles; third lower molar with one external 

 and one internal closed triangle, and one anterior and one posterior 

 obliquely transverse internal loop; plantar tubercles, 5; mammae, 6, 

 4 pectoral, 2 inguinal. 



307. guatemalensis (Microtus), Merr., Proc. Biol. Soc. Wash., xn, 



1898, p. 108. 

 GUATEMALAN MEADOW VOLE. 



Type locality. Todos Santos, State of Huehuetenango, Guate- 

 mala. Altitude, 10,000 feet. 



Geogr. Distr. Guatemala, Central America. 



Genl. Char. Size medium; color dark; tail short, with few hairs; 

 ears nearly hidden in fur. Skull: bullae large, swollen; incisive 

 foramina rectangular, truncate anteriorly and posteriorly; root of 

 zygoma anteriorly notched; jugals nearly parallel. 



Color. Upper parts mixed black and golden fulvous; under 

 parts slaty black; lips white; tail blackish, unicolor. 



Measurements. Total length, 155; tail vertebras, 40; hind foot, 

 21. Skull: occipito-nasal length, 26.5; Hensel, 23.5; zygomatic 

 width, 15; interorbital constriction, 4.5; length of nasals, 7.5; palatal 

 length, 13.5; length of upper molar series, 7. 



The next genus FIBER contains the Muskrats, the species most 

 familiar to man probably of all the Muridae, save those of the genus 

 Mus, which includes those species commonly called "house rats and 

 mice." The habits of the Muskrat resemble in a considerable degree 

 those of the Beaver, and their large-domed houses, formed of sticks, 

 roots, and grasses are often seen rising from the surface of a pond or 

 lake. The general plan of these structures is very similar to a 

 beaver's dwelling, and the entrance is beneath the water, with the 

 nest or sleeping apartment toward the roof so as to be, if possible, 

 above any sudden rise of the water. Holes in the banks by the side 

 of streams are often made, in which the Muskrat lives, and these 

 excavations sometimes cause the banks to cave in and a large portion 

 of ground to disappear beneath the stream. Muskrats are shy and 



