Hatfield-1934 Colo. R., Yzmi. N Calif.-Nev. Monument, 50 ft., Clark Co., Nev. 835 February 8, 1934 The runways are 8 cms. wide, on an average, where they are evident. We found only two evidences, that is to say, definite evidence, of nests or places in which the rats might nest. The nesting material (indicated on the map, p.33) was found loose and somewhat scattered through dead and fallen arrow-weed stalks. Since its disintegrated state was, to my knowledge, not due to human agency, it seems evident either that some carnivore pulled it out or that the rats themselves disposed of it when it was no longer in use. Since 4 young were caught in the tall grass area just to the north of the nesting material, I would be inclined to believe that and since the general area around this material was so overgrown as to make it difficult for a small carnivore to get at any nest, I would be inclined to believe that the latter theory was the more probable. However, we found no definite nest-site. The possibility has been suggested that this was a nest of Reithrodontomys.