. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 64 bulletin: museum of comparative zoology. stones occur at the top of the bed embedded in the overlying sandstone. No glacial striae or facets were seen on any of the exposed pebbles. Besides the sandstone pebbles, I saw one of micaceous quartzite, a crumpled phyllite, a whitish chert, a red argillaceous sandstone, a decomposed granite with reddish feldspar, a silicious schist, iti toto a variety of rocks indicating the derivation of at least a small portion of the debris from the Pre-Devonian terrane. The pebbles co
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 64 bulletin: museum of comparative zoology. stones occur at the top of the bed embedded in the overlying sandstone. No glacial striae or facets were seen on any of the exposed pebbles. Besides the sandstone pebbles, I saw one of micaceous quartzite, a crumpled phyllite, a whitish chert, a red argillaceous sandstone, a decomposed granite with reddish feldspar, a silicious schist, iti toto a variety of rocks indicating the derivation of at least a small portion of the debris from the Pre-Devonian terrane. The pebbles could hardly have been transported far by water action alone, because the sandstones pebbles are of a sort which do not wear well in any stream journey. I estimate their journey as stream pebbles to have been tens of miles rather than hundreds of miles. The assemblage of these pebbles in a well-stratified bed between layers of a coarse-grained sandstone leaves no doubt of water action. A few feet of sandstone separates this bed from the one above, in which the sandstones peb- bles again formed the predominant "constituents but were noticeably more rounded than the crystalline pebbles. Dr. I. C. White men- tions in his Report a bed of boulders at Ponta Grossa and a deposit containing fossil wood, but I saw none, nor were such deposits known to the Geological Survey staff at the time of my visit. Tilliie Bed at Conchas: â Conchas lies on the north side of the Rio Tibagy about four leagues west from Ponta Grossa. On the south of the village a small quarry was opened some years ago in a grayish somewhat in- durated stony clay bed, a boulder-clay phase of the tillite beds. The scattered pebbles consist of silicious rocks and rarely a granitic pebble. The bed fractures with a giant ball structure (Fig. 15). No striations were seen on the pebbles. The mode of occurrence of the pebbles seems best explained by dropping from floating ice and probably the clay with its sand grains of
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