CENOZoic (marine). 271 
overlying subdivision, the Lignitic has a rather characteristic 
invertebrate fauna, many new forms of which have been de- 
scribed by Mr. Aldrich in Bulletin No. 1 of the Alabama Geo- 
logical Survey. This, the Lignitic, constitutes our Lower Eocene 
division. 
Overlying the Lignitic and constituting our Middle Eocene are 
some 450 to 500 feet of strata which we for certain reasons sub- 
divide into two parts, the lower of which, 300 feet or more in 
thickness, has retained Professor Tuomey's name " Buhrstone," 
and the upper, 150 feet thick, the name of " Claiborne" from its 
best known and most characteristic exposure.* 
While we have not been able to point out any very well 
marked difference in the specific characters of the faunas of these 
two divistens, yet they differ widely in the relative abundance 
of their fossils as well as in their lithological characters. The 
Buhrstone is made up of claystones, aluminous sandstones, and 
quartzites chiefly, with an exceedingly meagre fauna represented 
for the most part by casts or moulds, while the overlying Clai- 
borne beds, consisting of sands and clays, hold a vast number and 
great variety of well-preserved shells. The Claiborne fossilif- 
erous sand, which is the name applied to a bed about seventeen 
feet in thickness, near the top of this division, is a yellowish 
ferruginous sand (originally a greensand), literally packed with 
the most perfectly preserved shells. It is this stratum which has 
furnished to the world most of the " Claiborne " fossils. It is 
doubtful if this bed is found outside of Alabama, or even at any 
considerable distance from the type locality, unless the main 
fossil-bearing bed at Jackson, Mississippi, be a representative 
of it.t 
The greater part of the Claiborne bed consists of calcareous 
* Dr. Hilgard includes both the Buhrstone and the Claiborne in his Clai- 
borne division, characterizing them as Siliceous Claiborne and Calcareous 
Claiborne, respectively. 
t The collections of Mr. Aldrich show that over fifty per cent, of the Jack- 
son shells are common also to the Claiborne fossiliferous sand ; but, on the 
other hand, Dr. Hilgard has found nearly every .Jackson shell, at some point 
or other, associated with theZeuglodon matrix, which lias usually been classed 
with the White Limestone. The occurrence of Aturea, a Claiborne form with 
the remains of Zeuglodon, will probably cause us to include the Zeuglodon-bear- 
ing beds with the Claiborne, which would increase the thickness of the Clai- 
borne to 210 feet and diminish that of tlie White Limestone correspondingly by 
about 60 feet. 
