Hattfield-1934 Colo. R., 1/2 mi. N Calit.-New. Monument, 500 ft., Clark Co., Nev. 336 February 8, 1934 But, in my experience, nests of harvest mice are much smaller and more compact. The area indicated on the map as "resting place" was a well-defined open space in the midst of a very thick clamp of tall grass. It was about 12in. in diameter, and had several runs leading into it. Its floor was covered with a layer of long grass stems neatly arranged. When I lifted this layer up I found numerous droppings under- neath it, indicating that the rats had spent some time there. It seems to me that these cotton rats are more localized than Microtus, being on the average more abundant per unit area. They do not have definite runs from one "island" of mesquite and tall glass to another, and it seems probable that they spend most of their time, most of their lives, even in one such island. For additional information, see notebook A H S Fitch for the same date.