June, 1912. 



New Titanotheres — Riggs. 



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out and being replaced by other ledges at 

 slightly different levels. The thicker ledges 

 are made up, for the greater part, of fine- 

 grained sands firmly cemented by calcareous 

 material, gray when freshly broken but 

 weathering to a reddish brown. In every 

 ledge there are traces of cross-bedding, 

 evidenced by diagonal veins of coarser 

 sands. Near the base or above a second 

 bedding plane, there is often a coarser layer 

 of river sand containing pebbles of quartzose 

 materials, sandstone, and clay shales. This 

 layer is invariably cross-bedded, often inter- 

 rupted and replaced at nearly the same level. 

 In these coarser strata occur as fossils dis- 

 articulated bones, branches and sometimes 

 trunks of trees. In the upper series the 

 sandstones weather into vertical, or often 

 over-hanging walls, with accumulations of 

 fallen blocks at the base. (PL V, Fig. 1.) 

 In the lower levels they are quite as often 

 exposed in steep slopes half covered with a 

 shaly talus. Many of the calcareous ledges 

 disintegrate where exposed to the weather- 

 ing agencies and flake away more rapidly. 

 These two series, designated as Lower 

 and Upper Metarhinus Zones, include, as 

 nearly as the writer can determine, Horizon 

 A of Peterson and Osborn. Probably they 

 include a little more than was originally 

 so designated. The lower division is best 

 defined as including the whole of those sand- 

 stones in which the genus Metarhinus occurs. 

 This genus is by far the most distinctive fos- 

 sil of this horizon and is apparently confined 

 to it, though at certain levels Dolichorhinus 

 was found equally abundant. In the three 

 months of careful work and record by our 

 party no trace of Metarhinus was found 

 above the sandstones described. However, 

 the habitat of this animal appears to have 

 limited its occurrence to the river sands. 



