PEBBLE PHOSPHATE DEPOSITS. 
73 
The presence of rhinoceroses in the formation is believed to 
establish definitely the fact that the beds cannot be later than early 
Pliocene, since rhinoceroses in America apparently did not survive 
beyond that time. 
A few horse teeth have been obtained from the pebble phosphate 
beds, all of which are referable to the genus Hipparion , horses of 
the modern genus Equus not being present. 
The tree trunks which are occasionally found silicified both in 
the phosphate beds and the overburden no doubt floated in from 
the nearby shore, or were carried in by streams. The cellular struc¬ 
ture of the wood is not well preserved and the species has not been 
identified. 
Turtle remains are found not infrequently in the Bone Valley 
formation. As a rule scarcely more than fragments or plates from 
the carapace are found. The Phosphate Mining Company, how¬ 
ever, fortunately recovered a considerable part of the carapace and 
plastron of a very large land tortoise from their pit at Nichols. This 
specimen has been presented to the State Geological Survey and is 
preserved in the State Survey collection. An illustration of the 
specimen is given on page 70. 
MARINE AND ESTUARINE FOSSILS OF THE PHOSPHATE BEDS. 
The marine fossils of the phosphate beds include several verte¬ 
brate types and a few invertebrates. The aquatic vertebrates' in the 
formation include cetaceans, crocodilians, and fishes. The most 
common cetaceans are long snouted forms belonging probably 
in the family Platanistidae. Fragments of the skull and jaws, 
and also the vertebrae are not uncommon. It seems probable also 
that the broken ribs found in such abundance in the phosphate beds 
pertain to these small cetaceans. 
Crocodilian teeth, vertebrae and bones are not uncommon in 
the phosphate beds, and the members of this order were no doubt 
abundant in the shallow waters in which the land pebble phosphates 
were accumulating. Among the best preserved of the specimens 
that have been obtained is a part of the upper and lower jaw of a 
gavial from the pit of the Amalgamated Phosphate Company, pre¬ 
sented by the Company to the State Geological Survey. The species 
being new, the writer has suggested for it the term Tomistoma 
cimericana * The discovery of these fossils in the Bone Valley for- 
*A New Gavial from the Late Tertiary of Florida. Amer. Jour. Sci. xl, 
Aug., 1915. 
