The Passasimas, Siakumne, and Seguamne were situated in the vicinity of the San Joaquin River and hence were more exposed to the Spanish expeditions than the tribes along the lateral streams. Hence the proportion of those taken for conversion may have been higher than the 10 per cent of the aboriginal population found for the Cosumnes, although it would not have attained the value of 50 per cent characteristic of the more westerly delta tribes. We may take an intermediate figure, 20 per cent. This would give the Passasimas a population of 725, the Siakumne 110, and the Seguamne 815. The great disparity between the figures for the last two tribes may well be due to confusion of names in the mission records. The total for the three is 1,650. For the Yatchikumne on the Calaveras River no more than 10 per cent baptisms can be assumed, yielding a population figure of 1,180. If only geographical location were considered, the same factor could be used for the Moquelumnes but this tribe resisted missionization with extraordinary tenacity. Hence we are not justified in using a factor of more than 7 per cent, from which we may infer that the population was 2,040. The baptism data would then give us a total for the group of 4,870. According to the estimates furnished by pioneers and government officials for the period just preceding the Gold Rush the population ran into the thousands. The census by Savage (Dixon, MS, 1875) puts 4,000 on the Cosumnes, Mokelumne, and Calaveras and 2,500 on the Stanislaus, F. T. Gilbert (1879, p. 13) says that "before the advent of Sutter" there were 2,000 on the Mokelumne and, as far as I can ascertain, he implies that on the Cosumnes and Mokelumne together there were fully 5,000. These figures were undoubtedly greatly exaggerated but nevertheless indicate a very large population in the area just before the discovery of gold and subsequent to the destructive epidemics of 1833-1835. Even if we cut these estimates in half, there would remain in midcentury approximately 2,000 persons in the basins of the Moquelumne, Calaveras, and adjacent San Joaquin rivers. A residue of 2,000 in 1850 means certainly an original population of three times as much, i.e., 6,000. To recapitulate the estimates for the Moquelumne group, we find: By stream densities 7,200 By adjusted tribal averages 4,800 By baptism data 4,870 By extrapolation from American estimates 6,000 _______ Mean 5,720 The mean, 5,720, appears entirely reasonable for the aboriginal population of such a vigorous and important group. Moquelumne group ... 5,720 __________________________