﻿418 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr: 10, 



and presenting a very rough surface from the floundering of the 

 large herds of buffalos in the tough 

 plastic clay bottom as they had been 

 eagerly striving for the last trace of 

 water. These clay beds, which con- 

 tain a large proportion of calcareous 

 matter and are often " banded" by 

 thin seams of soft ironstone, have a 

 white chalky aspect, and are so easily 

 acted on by the weather that what 

 were originally gulleys soon expand 

 into wide flats bounded by conical 

 hills, with bright surfaces marked 

 regularly at every few inches by the 

 parallel streaks of ironstone, which 

 are often only half an inch thick. 

 From these swampy flats, that serve 

 as reservoirs for the water which de- 

 scends from the bills in spring, the 



streams have worn deep ravines which 

 join the valley of Eed Deer River. At 



the commencement of one of these, 



or near the base of the group C, the 



"banded clays" were seen to rest on 



red iron-clay shales in thin beds, 



underneath which is a bed of rotten 



limestone of a buff colour, which again 



rests on a bed of shell-conglomerate, 



principally composed of fragments of 



Ostrca cortex aggregated into a solid 



rock with many complete specimens of 



the same shell. Mr. Etheridge has 



identified this shell, which is a spe- 

 cies described by Conrad in the Mex- 

 ican Boundary Commission Reports 



(p. 157). Together with Ostrea mid- 

 til i rata it was found at Dry Creek, 



Mexico ; and, in describing them, 



Conrad says that he knows no species 



like them in the Cretaceous System, 



and that probably they belong to 



strata of still earlier date. However, 



at another locality, near the Hand Hills, 



I again found Ostrea cortex, and along 



with it 0. vellicata and Cytherea 

 Texana ; and these are undoubted 

 Cretaceous shells of Mexico. From 

 between El Passo and Fontera, which 



seem to be places within a few miles of each other, the following 

 list of fossils is quoted in the Mexican Boundary Report — 0. velli- 



•jaa; 009 



