25G 
FOSSIL TURTLES 
with which the trionyx is covered, may be firmly 
attached.* Being destitute of scales, their bones 
exhibit no traces of the furrows, or depressions, 
produced by their margins, as in the other sub- 
genera. The fossils we are about to describe, 
possess a shagreen surface, like the trionyx, but 
differ from the recent species in bearing decided 
marks of having had a scaly covering. In the rib 
above represented these impressions are clearly 
shown ; and it is necessary to remark, that this 
bone, instead of being nearly of an equal width 
throughout, as in the fresh-water and marine spe- 
cies, gradually enlarges till the outer termination 
is nearly twice as wide as the inner. Such a 
character obtains in the ribs of land tortoises only t, 
and therefore presents another anomaly in the struc- 
ture of the fossil animal. Portions of the sternum 
or and some of the scales belonging to this 
species, have been found. Large bones, covered 
with little pits, or fossae, as in the soft turtles, have 
also been discovered ; but they are too imperfeci 
to be identified except by more experienced com- 
parative anatomists than ourselves. From the 
slight degree of convexity of the rib, it is clear 
that the original was of a flattened form, like the 
common turtle, 'Festudo mydas ; the shagreened 
surface proves its analogy to the trionyx ; but the 
impressions of the scales show that it cannot be 
identified with any recent species. It may be men- 
tioned, that among the numerous portions of the 
* Oss. Foss, tomeiii. p. 3?9. 
t Oss. Foss., tonic iii. p. 3.33. Edit. 1822. 
