VERTEBRATES FROM MIOCENE, PLIOCENE AND PLEISTOCENE. 91 
Subsequently the Alum Bluff formation was placed in the Oligocene 
following the general acceptance of that term in America. 
The top surface of the Alum Bluff formation at Alum Bluff is 
eroded, the later formations resting unconformably upon it. A 
better section of this formation is seen at Rock Bluff, seven miles 
farther up the river, where about 90 feet consisting chiefly of phos- 
phatic and calcareous sands similar to those at Alum Bluff are re¬ 
ferred to the Alum Bluff formation. In this section the fuller’s 
earth stratum comes in near the top of the exposure about 100 feet 
above the river. From this locality to the fuller’s earth mines in 
Gadsden County and thence into Leon County the Alum Bluff for¬ 
mation is continuous and affords frequent exposures. 
The invertebrate fossils found at the fuller’s earth mines near 
Quincy, in Gadsden County, on the basis of which the deposits have 
heretofore been referred to the upper Oligocene, include the fol¬ 
lowing :* 
Cyprsea, agreeing in form and size with C. pinguis Conrad from the Chipola 
horizon. 
Murex mississippiensis Conrad? var. 
Fulgur spiniger Conrad? 
Modulus sp. 
Crucibulum auricula Gmelin. 
Area staminata Dali. 
Pecten (Nodipecten ?) sp. 
Cardita serricosta Heilprin. 
Chione sp. 
Carolia floridana. 
In view of the previous reference of the Alum Bluff formation 
to the Oligocene on the basis of the invertebrate fossils it becomes 
particularly interesting to compare the vertebrate fossils which have 
now been obtained, from the formation. 
AGE OF THE FORMATION AS INDICATED BY THE VERTEBRATE FOSSILS. 
Among the vertebrates the most characteristic as well as the 
most valuable for stratigraphic purposes are the horses. The genus 
Merychippus is regarded as a characteristic Miocene horse, its 
range being from middle (or lower) Miocene to lower Pliocene. 
The genus Parahippus first appeared in formations which are near 
* Vaughan, T. W., Mineral Resources, U. S. Geol. Surv., 1901, pp. 929-930. 
1902; Fla. Geol. Surv. Second Annual Report, p. 98, 1909. 
