^54 
ORGANIC REMAINS 
5. Radii, or dorsal defences, of a fish allied to 
the Silurus. These occur of three or four species, 
and very closely correspond to the bony fin of the 
recents Silurus.* 
6. Minute scales and vertebrae : some of tlie 
argillaceous partings of the strata are full of these 
remains, but they are always in too mutilated a 
state to afford correct indications of the forms of the 
originals. 
CHELONIAN REPTILES, OR TURTLES. 
The disjointed bony skeletons are, with but few 
exceptions, the only remains of turtles that occur 
in a fossil state ; and it is therefore by a careful 
comparison of the fossil with the recent bones that 
we can alone hojie to obtain satisfactory conclu- 
sions respecting the forms and habits of the ori- 
ginals. Among the osseous remains of this order, 
which have been discovered in the strata of Tilgate 
Forest, none have been found in so perfect a state 
as to exhibit any considerable portion of the upper 
shell or carapace : but the detached ribs, vertebrae, 
portions of the bones of the sternum, pelvis, and 
extremities, which are abundantly distributed both 
in the Tilgate stone and in the friable sandstone, 
will, with the light which the illustrious Cuvier 
has thrown upon the anatomy of the recent ani- 
mals, enable us to obtain highly interesting results. 
* The Silurus gla7iis inhabits the rivers of Europe and the East ; it 
is the largest of all freshwater fishes, being frequently twenty-four feet 
long and weighing 300 pounds. Elements of Nat. Hist., vol. i. p. 368. 
