Vol. V] TAYLOR—NEW SUBGENUS OF PHENACOMYS \^g 



Wilder writes that he has found mud-masses in some of 

 the nests, and that the foundation of a fresh nest recently- 

 examined by him was of small dry branches and mud balls. 

 In mentioning these facts, he suggests that possibly the nests 

 containing mud are built upon structures started by some 

 mud-mason like the robin, or possibly a wood rat, which 

 makes use of anything loose it can find. 



More extended reference is made below (see page 1.53) to 

 the possibility of the existence of two kinds of nests, "male" 

 nests and "family" nests. Clay has submitted the following 

 description of the supposed nest of the male : "The male 

 nest is a neat, compact, round ball of small twigs, five to 

 eight inches in diameter or possibly a little larger, well lined 

 with the usual material, containing one entrance hole as a 

 rule, the opening facing the trunk of the tree and usually 

 being well hidden by foliage. The favorite location is one 

 where the fir needles are thickest on the limb, some distance 

 away from the trunk of the tree. Annual additions were not 

 in evidence in any of the male nests examined. Ordinarily 

 only one nest is to be found in a tree, but in several instances 

 in which the family tree was isolated the male's nest was 

 found in the same tree with the family nest. The nest of the 

 male is always higher in the tree than the family nest, and is 

 usually well concealed." 



(c) The inner nest cavity 



All inner nest cavities examined by us were lined either 

 with net lichen or with the fine fir-leaf resin ducts. In spite 

 of the humidity of the surroundings and the dank character 

 of the nest mass below it, this inner nest appeared to be dry 

 and comfortable. The finely shredded character of the mate- 

 rial used for the inner nest guarantees its softness, and the 

 thickness of its walls probably insures a certain degree of heat 

 in occupied nests. It is even possible that the slow oxidation 

 of the nest-mass, as indicated by the sweating nature of the 

 material beneath the occupied nest cavity, is a source of heat. 



The cavity of the nest at Lierly's Ranch from which the 

 tree mouse was secured was 10 inches across. It was always 

 necessary to dissect away much outer material before the 

 inner nest could be found. Located in the upper part of the 

 nest as a whole, it was in all -cases covered over and well pro- 

 tected from the outside. 



