198 NORTH AMERICAN FAUNA [No. 55 



both night and day, or about 2,400 Douglas fir leaves weighing 

 about 18 g in 24 hours. 



Normally these green leaves must furnish both food and moisture 

 as the mice refused water except when forced to eat dried leaves. 



Economic status. In a large number of tree nests examined in 

 Oregon no trace of injury to the trees or foliage was found and no 

 complaints of injury have been reported. It is possible that the tree 

 mice may have a slight value as food for martens and fishers, the 

 two species of tree-climbing fur-bearing animals of the region, and 

 they have certainly added a feature of living interest to these mag- 

 nificent forests of the Pacific slope. 



PHENACOMYS SILVICOLA A. B. HOWELL 

 DUSKY TREE MOUSE 



Phenacomys silvicolus A. B. Howell, Jour. Mammal. 2 : 98, 1921. 

 Phenacomys silvicola Miller, U. S. Natl. Mus. Bull. 128 : 400, 1923. 



Type. Collected 5 miles southeast of Tillamook, Oreg., by Peter P. Walker, 

 October 25, 1916 (collection of Alex Walker). 



General characters. Slightly larger and much darker than Phenacomys 

 longicaudus but with the same general proportions of total length, tail and foot, 

 the same hairy tail and long soft fur; ears small, not projecting much beyond 

 the fur; skull long, narrow, ridged, and with heavy molar teeth. Color dark 

 brown ; upper parts sayal brown of Ridgway, the long hairs sparsely tipped with 

 black ; lower parts washed with whitish ; nose dusky ; tail blackish ; feet dark 

 gray. 



Measurements. Total length, 191 mm; tail, 81; foot, 22; ear (dry), 10. 



Distribution and habitat. The type was found dead on a log on 

 a ridge covered with first-growth Douglas fir near Tillamook (fig. 

 41). Other specimens from near the type locality were later col- 

 lected by Alex Walker, and one other adult and four young were 

 taken by H. M. Wight from a nest in a tree near Corvallis. 



The limits of its range remain to be established. At present it is 

 one of the rarest and most interesting of Oregon mammals, present- 

 ing problems to baffle as well as tempt the most daring naturalists. 



Walker contributes the following notes : 



The type specimen of Plienacomys silvicola was taken near Tillamook, Ore- 

 gon, October 25, 1916, and remained unique until 1924 when a female and 

 four small young were taken from a nest in a tree near Corvallis, Oregon, and 

 recorded by H. M. Wight (Journ. of Mammalogy, vol. 6, p. 282, 1925). I am 

 now able to record two more specimens of this rare species. 



On February 1, 1926, my brother, Peter P. Walker, who secured the type of 

 Phenaoomys silvicola, presented me with another specimen in the flesh, taken 

 6 miles south of Tillamook under the following circumstances. Employees of 

 the Coates Driving and Boom Co., in the course of their logging operations, 

 removed by blasting a hemlock snag about 2 feet in diameter and 20 feet high. 

 Quite a hole was blown in the earth under the stump, and immediately after 

 the blast workmen saw 4 or 5 mice in this excavation. My brother, who was 

 employed by the company, captured one of the mice but the others escaped. 

 Fragments of what was unquestionably the nest were noted at the time. On 

 the following day I visited the place but the shattered pieces of the snag had 

 been removed and no trace of the nest could be seen. However, while examin- 

 ing the debris in the pit, the somewhat mangled remains of another tree mouse 

 was found, this one undoubtedly having been killed by the blast. 



On examination the hemlock snag was found to be hollow, and the cavity, 

 though small, extended the entire length. Now from the fact that immediately 

 after the explosion several of the mice were noted alive in the pit, it is ap- 

 parent that they must either have had a nest underneath the stump, or, as 



