. Anniversary memoirs of the Boston society of natural history ; pub. in celebration of the fiftieth anniversary of the Society's foundation. 1830-1880. Natural history; Indians of North America. Section The dip of the strata is quite irregular, considering the limited boundaries of the pits, varying from 10° to 30° of inclination outwards on all sides of the central hill. This elevation, to a certain extent, evidently took place before the formations of the pits were entirely completed. This is shown by the pocket containing the PI multiformis and PI. discoideus shells in the New Pit, and
. Anniversary memoirs of the Boston society of natural history ; pub. in celebration of the fiftieth anniversary of the Society's foundation. 1830-1880. Natural history; Indians of North America. Section The dip of the strata is quite irregular, considering the limited boundaries of the pits, varying from 10° to 30° of inclination outwards on all sides of the central hill. This elevation, to a certain extent, evidently took place before the formations of the pits were entirely completed. This is shown by the pocket containing the PI multiformis and PI. discoideus shells in the New Pit, and also by a similar pocket in the East Pit. Formations m and x 2 of Section 9 were evidently de- posited one upon the other in the New Pit. The only way to explain the appearance of the wood-cut, after this, is to imagine that the fold- ing took place along the lines of elevation. The wood-cut represents a section at right angles with the dip, so that the folds run across the strike of the layers. Subsequent to the folding, a certain amount of denudation must have removed part at least of the bed x 2, and the upper part of the bed m, in order to permit the deposition of n 0, and x 3. Whether the same tendency to fold continued, caused by the resumption of the process of elevation on either side of x 3, and gave the basin-shape to n o, deepened the folds on either side, but did not alter them otherwise, leaving x 3 a symmetrical hollow, or saucer-shape, is doubtful. They seem to belong to the same system of folds as X 2 and the want of x above is probably due to local denudation. On the face of the pit on the north side of x 3, this is shown by the anticlinal bend in m, but even more perfectly by the fact that n o, and m become exactly parallel farther to the north. Section 10 shows that some- what similar conditions must ^H have obtained in the East Pit at about the same time. Un- fortunately I had confused the samples from x 1, with those from k, and consequently only rely on
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