Thaeler 1958 Species account Microtus californicus July 16 Vallecitos Stage Station, 5005 ft., San Diego Co., Calif. This morning I had one of these, a female, in one of the twenty-five traps I set in a marshy area behind the stage station. There is an area of several acres of marshy area here which is covered, even in mid-summer, by green vegetation - mostly various grasses. Microtus sign is not overly abundant. Sept. 18 1.0 mi. N, 2.0 mi. E Mantiguay (saltmarsh), Contra Costa Co., Calif. This A.M. I had four mice. (None yesterday). Microtus sign is virtually non-existent in the areas of the marsh I have looked at. I had over 200 traps in Salicornia and saltgrass (Disticalis). The Salicornia here is not too high and often there is a layer of matted vegetation about an inch or two [even 3] above the ground. I didn't see any Salicornia cuttings. Sept. 20 One Microtus this A.M. After hunting around further in the marsh I began to find some Microtus sign, both feces and cuttings in areas where the weed covered tall rushes. Under these there is some a little grass (not Disticalis) and Salicornia. The best sign was found in areas where it was v. moist, even areas flooded at high tide. I moved most of my traps into these areas. Sept. 21. I had two Microtus this A.M. along with lots of toads and a couple of crayfish.