This concept of the original status of aboriginal units in northern Contra Costa County is at variance with the arrangement postulated by Schenck, who places the "Tarquimenes" and the "Tarquimes" eastward across the delta islands nearly to Stockton. There is some reason to believe that many of these delta islands were aboriginally uninhabited, but wholly apart from this consideration, another explanation can be offered, which has been suggested by Schenck (1926) and by the present writer (1955). It rests upon the probability that many of the delta tribes had undergone extensive migration, owing to Spanish military pressure in the period from 1785 to 1810. Thus the Karquines of the early accounts may have moved east along the south shore of Suisun Bay, far into the delta, and hence may have been recorded by later visitors under a series of name variants. In the meantime the Chupunes, or Chupkanes, may have been pushed southwest, as intimated by Kotzebue (cited by Schenck, 1926, p. 130). It is pretty clear that the tribal territories as reported by a succession of explorers from 1805 to 1820 did not conform to the aboriginal pattern. Our best solution, for present purposes, is to consider the strip from Crockett to Port Chicago as having been the range of the Karkin. _Area 4. The interior valleys from Lafayette to Walnut Creek and Danville._--Part of this region was traversed by Fages and Crespi, who reported several villages. It is later identified as the home of the Saclanes. This tribal aggregate first comes into prominence in 1795 in connection with the murder of the San Francisco Christians, who slept on the beach and reached the Saclanes by noon. Amador, on his expedition of 1797, reached them in less than twenty-four hours from Mission San José. Other documents, cited previously, indicate that in spite of terminal disorganization and scattering the original home of the group was in the small valleys west of Mt. Diablo. The linguistic evidence adduced by Arroyo de la Cuesta (1837) demonstrates that the Saclanes were a non-Costanoan people, perhaps related to the Plains Miwok. This identification as Miwok, was first made, on the basis of the de la Cuesta vocabulary, by A. S. Gatschett, was verified by C. Hart Merriam, and first published by M. S. Beeler (1955). Kroeber (1925) classes Saclan as doubtfully Costanoan, but shows the group as Costanoan on his large colored tribal map. Regardless of their linguistic affiliation, however, historically and ecologically they must be considered as in the same position as the Costanoans who surrounded them. The mission records are explicit. The tribe, at least under the usual name, was converted at the San Francisco Mission and no other. The first baptisms occurred in 1794 and the last in 1798.