304 NEW MOUSE FEOM OREGON TEUE. 



Measurements of the skull. — Length of the crowns of the upper series 

 of molar teeth, 5,8™™; lower molars, 5.7™™; length o^ nasal bone, 

 6.G™™; breadth of iuterorbital construction, 2.8™™. 



The molar teeth resemble those of P. intermedius, but the lozenges 

 are narrower, and the external re-entrant folds of enamel in the upper 

 molars are directed less backwards and those of the lower molars less 

 forwards than in that species. The molars are rooted. The skull is 

 that of a youngish individual. 



Habitat. — Marshfleld, Coos County, Oregon. 



Regarding the habits of this mouse, Mr. Todd, in a letter to Professor 

 Langley, writes as follows : 



By mail to-day I seud you a skin and skull of a tree mouse. It lives exclusively, 

 as far as I have been able to ascertain, among the boughs and branches of the Oregon 

 pine trees {Abies Doiiglassi), making a nest of a size smaller than a robin's nest. It is 

 usually situated on the upper side of a medium-sized branch, perhaps 6 inches in 

 diameter, and is composed of the leaves of the tree deftly split in two from one end to 

 the other and dried. The nest is neatly and rather ingeniously made, and the sameness 

 of the material is a novelty. I have only seen two of these mice— one from Doug- 

 las County, and this one from Marshfield, C003 County— though I have seen a large 

 number of their nests in this county (Lane County), as well as in Curry, Coos, and 

 Douglas. I can get no information from any one regarding them either from 

 scientiiic sources or from the observations of others. 



The mouse is almost exclusively arboreal in its habits, but I think that I have 

 reason to believe that they sometimes come to the ground for food, as I have seen 

 tracks in the snow around the trees which I think were made by these little animals. 

 They could be tracked up and down the tree, but to no great distance from it, and 

 were most likely in search of food. 



It is entirely distinct from Arvicola and every other mouse that I have ever seen.. 

 I have lived here for many years, and may, perhaps, be considered a close observer. 



National Museum, September 10, 1890. 



