1875.] 209 [Hoflman. 



It has not been thought advisable to attempt to identify all .of 

 Ehrenberg's species, as his plan was to found a species upon any 

 variation in the number of rays in the circular forms of the Diatom- 

 aceas, a principle now generally rejected. 



One striking fact is the great abundance in all the layers of 

 Galionella sulcata Eh. == Orthosira marina W. Smith, which is more 

 numerous in some slides than all the other forms together. 



December 15, 1875. 



The President, Mr. T.T. Bouve, in the chair. Sixteen 

 persons present. 



The following papers were read : — 



Ancient Hearths and Modern Indian Remains in the 

 Missouri Valley. By W. J. Hoffman, M. D. 



ancient hearths. 



The Military Station at Grand River, D. T., is situated upon the 

 western bank of the Missouri River about midway between Fort 

 Sully and Fort Rice: approximate location, long. 100° 12' W"., 

 lat. 45° 31' N. About three hundred yards from the river the 

 bottom-land is walled in by a range of bluffs, about one hundred 

 and twenty feet in height, the upper surface of which corresponds to 

 the level of the surrounding prairie. Three quarters of a mile below 

 the station, Oak Creek empties into the Missouri River, thus forming 

 a low head-land or spur, the ridge of which still bears evidence of 

 aboriginal occupancy. Grand River empties into the Missouri from 

 the west also, three miles below the station, where the Mound Build- 

 ers once threw up earthworks, traces of which are still visible. 



During the spring flood of 1873 about twelve feet of the embank- 

 ment at the station was washed away, exposing to view two distinct 

 river beds. The height of the embankment is twenty-two feet. The 

 upper stratum, which was composed chiefly of sand and gravel, was 

 ten feet thick, resting upon the fine sand of the upper surface of the 

 second stratum. Throughout the bottom of the upper stratum was 

 deposited an indiscriminate mixture of branches, trunks and stumps 

 of trees, consisting chiefly of cottonwood, oak and cedar. The second 

 stratum was six feet thick, also consisting of coarse sand and gravel, 



PROCEEDINGS B. S. N. H. — VOL. XVIII. 14 FEBRUARY, 1876. 



