1323, 329, 830 1 ] BLUFF formation— fossils. 195 



observed only in a few places where the terraced form of slowly 

 denuded hillsides showed the existence of a certain horizontal 

 structure. 



Wherever these beds occur associated with the Orange Sand strata, they 

 overlie the latter ; being in their turn as uniformly overlaid by the yellow or 

 brown surface loam, which in the rest of the State, reposes directly upon the 

 Orange Sand (1[332). The thickness of the Bluff formation is very variable, 

 its materials having, apparently, filled up the valleys, resulting from denudation 

 in the older formations — the Tertiary, and Orange Sand. Its fossils, so far as 

 known, are exclusively terrestrial. 



328. In the Southern River Counties, below Vicksburg, the deposits of this 

 formation are found on a belt ten to fifteen miles in width, running parallel, in 

 general, to the Mississippi River ; the surface is very much broken by deep and 

 steep valleys and ravines, which always result from the denudation of these 

 deposits. Intimately connected as these are with the agricultural features of 

 this region, I shall refer the reader, for further details on the subject, to the 

 description of the Southern River Counties, in the Agricultural portion of this 

 Report. As to its region of occurrence north of Vicksburg, along the Missis- 

 sippi Bottom, I cannot speak from personal knowledge. It appears from scat- 

 tered observations recorded in Harper's Report, that the silt of the Bluff forma- 

 tion appears in patches or limited belts, along the border of the hills, from 

 Satartia on the Yazoo to the Tennessee Line ; not extending back into the inte- 

 rior, for more than a few miles at most. The character of the deposit is described 

 as being in all respects the same as that exhibited in the Southern River Coun- 

 ties, save in that it is overlaid here by a }*ellow Io:tm containing calcareous 

 concretions; which is not the case below Vicksburg, where the loam (see anal- 

 ysis under Southern River Counties, Agr. Rept.) contains no more lime than is 

 necessary to constitute a good soil. Possibly this calcareous loam may be a dis- 

 tinct facie.s of the Bluff formation itself, or the link of connection between it 

 and the common brown surface loam, which is elsewhere wanting. 



o2;i. Fossils of the Bluff Formation — These, as has been mentioned, 

 are altogether terrestrial, so for as asceitained. 1 have given but little atten- 

 tion to their study as yet; but the shells have been collected by Prof. Wailes, 

 aud studied by him ; they, as well as the mammals, having received the atten- 

 tion of Conrad and Leidy, in part through specimens furnished by Prof. Wailes. 

 The snails occur singly, imbedded in loose silt, or not unfrequently, in the 

 calcareous concretions above mentioned ; at times they appear in bands or strings, 

 disposed, however, without any apparent regard to stratification. Their sub- 

 stance, although softer and more friable than in the living individuals, sometimes 

 preserves the stripes or markings of the surface very distinctly. 



The bones, as well as the ivory of the Mastodon's tusks, are mostly soft and 

 friable, having lo-^t the greater part, or all of their organic substance ; so that on 

 drying they crumble or exfoliate, unless previously imbued with a solution of 

 glue. It seems that these boHes have in most cases been much scattered, so 

 that they are generally found singly. Considerable portions of the skeleton 

 have, however, been found together in spots where ponds would seem to have 

 existed, as though the animal had perished there ; and in such cases the bones 

 are frequently in contact with considerable masses of black, fatty earth, which 

 may reasonably be supposed to have resulted from the decomposition of the 

 viscera, and other perishable animal matter. (Wailes). 



330 1 The snails all seem to belong to living species, though, according to 

 Prof. Wailes, some of them are not at present living in the region where they 

 occur in a fossil state. Among the specimens obtained, Prof. W. mentions the 

 following (First Rept., p. 283) : 



