Hooper Reithrodontomys halicoetes 1 mi. W Avon (salt marsh), Contra Costa Co., Calif. Feb. 28, 1937 Traps baited with oatmeal and placed in Microtus runways yielded at least 4 R. halicoetes. They were found in the same immediate area with R. megalotis. On at least one instance one trap contained a megalotis and the next trap, about ten paces away, held a halicoetes. As I look at the skins of harvest mice all collected in the same marsh and on the same trap line, it seems to me that 4 are R. megalotis and 4 R. halicoetes. On the same line were caught Mus musculus, Sorex sp? and Microtus californicus. St. Vincent, salt marsh, 3 mi. N San Rafael, Marin Co. May 25, in 58 traps Caught 1, set in runways in Salicornia. This one was caught where the pickle weed was thick and the ground moist. All but about 3 of the other traps were set where one of the other of the above "factors" was not satis- fied.