Through the generally hilly interior of Alameda and Contra Costa counties there are but two areas of sizable extent in which preconquest village sites occur with relative frequency. One is the Lafayette-Walnut Creek-Danville region and the other the Livermore Valley, west to Pleasanton and Dublin. These provinces were inhabited in the late eighteenth century by the Saklan and Seunen respectively, and are so designated on the map. Indeed, the correspondence between archaeological sites and the occurrence of rancherias in early colonial times is remarkably close. The conclusion is permissible that the pattern of occupancy found by the Spaniards had been established long previously and was fully stabilized at the time of their arrival. This condition in turn argues a mature balance between the natural environment and the indigenous population. BIBLIOGRAPHY _Abbreviations_ BAE-B Bureau of Ethnology, Bulletin UC University of California Publications -AR Anthropological Records -PAAE American Archaeology and Ethnology Abella, Fr. Ramón MS Diario de un registro de los Rios Grandes. Oct. 31, 1811, San Francisco. Bancroft Trans., Santa Barbara Arch., IV: 101-134. Bancroft Library, Berkeley, California Arroyo de la Cuesta, Fr. Felipe MS Lecciones de Indios. Bancroft Library, No. C-C 63a. This document is one of several handwritten manuscripts left by Arroyo de la Cuesta. Beeler, M. S. 1955. Saclan. Internat. Jour. Amer. Ling., 21: 201-209. Bolton, Herbert E. 1926. Historical Memoirs of New California, by Fray Francisco Palóu, O.F.M. 4 vols. Univ. Calif. Press, Berkeley, California. 1927. Fray Juan Crespi, Missionary Explorer on the Pacific Coast, 1769-1774. Univ. Calif. Press, Berkeley, California. Crespi's Diary of the Fages Expedition is translated by Bolton on pp. 277-303. 1930. Anza's California Expeditions. 5 vols, Univ. Calif. Press, Berkeley, California. Vol. III contains Bolton's translation of the Anza diary of the second Anza Expedition (pp. 1-200) and Font's short diary (pp. 201-307). Cañizares, José de 1775. Letter to Ayala, September 7, 1775, San Francisco. Archivo General de Indias, Seville, Spain. Papeles de Estado 20 (Mexico). Microfilm in the Bancroft Library, Berkeley. Roll II, Reel 3M715, pp. 24-32 inclusive. MS Map, 1775: Piano del Puerto de San Francisco, registrado por el Paquebote de S.M. San Carlos al mando el Theniente de Fragata de la Real Armada Don Juan Manuel de Ayala en este año de 1775. Photostatic copy in Bancroft Library, Berkeley, of a manuscript map on file at the Library of Congress. Said by Henry J. Wagner (1937, II: 342) to have been drawn by Cañizares.