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74 [Continued from p. 62] 1. Astraponotense. 2. Upper Notostylopense. 3. Upper Notostylopense (the pink parts) And also Astraponotense (the channel gravels). In the latter case Ameghino's Upper Notostylopense + Astraponolense of Coli-Huapi are the same, which seems quite possible in the field, as nothing below checks even re- motely with his data for the U.Notos.+ nothing above checks well with his data for Astraponotense. Between this and the next gravels we have only one specimen, #94. Lava + Upper Channels: Regarding the channel beds, it is necessary to distinguish between the hard tuffs weathering yellow to orange with vessicles, + true conglomerates. The hard beds are usually but not invariable associated with or part of a true channel series. On the other hand channel gravels may also occur (as lower half of p. 4) without associated hard beds. Gravels appear from 30' to 100' above that of the so-called lower channel. Where most powerfully developed(west end of barranca, e.g. prof. p. 6, p. 22) they have a thickness of over 100', with recurrent conglomerates + numerous local unconformities, overlain by the hard orange beds which also contain some gravel. These are of course highly variable and grade laterally into tuffs with few or no true gravel beds and no visible unconformities, although usually one or two pebble horizons remain. 75 There are large lava flows at each end of the barranca and various small tongues seen in section near the west end. Contrary to my first belief, these are not at exactly the same level. They rest in small valleys on the eroded surface of the underlying beds and the slight differences of level may be due purely to that fact. Their presence does not necessarily indicate an important unconformity as similar erosion surfaces are indicated equally clearly (or obscurely) at various other levels in this channel series. Whether or not these are the result of one eruption, there were lava flows in this region previously for in one or two spots pebbles of vesicular lava were found in place in cg. at least 30' below the surface on which a local flow rests. Except for these, which are nowhere numerous, the gravels are all of materials which could be derived from the beds below them, chiefly hard tuff pebbles. It seems reasonable to conclude that in this area there was a fairly prolonged period of extrusion of lavas and that it coincided with the channel deposit in general. The only fossils found in this part of the series were fairly numerous fragmentary remains of a very large Parastrapothere and a few fragments of Pyrotherium, although none of the latter found by us happen to have been in place. The top of the lava flows is not coincident with the Pyrotheriense- Colpodonense boundary. The location of This cannot be fixed within a few feet At any one locality, but occurs within