257 
TRIONYX EMYS. 
the principles of their construction, with tlie 
conditions by which existing Turtles are fitted 
tor their marine abode, that Cuvier was at once 
enabled to pronounce these fossil species to have 
een indubitably inhabitants of tlie sea.* 
The genera Trionyx and Emys, present their 
lossil species in the Wealden freshwater forma- 
ions of the Secondary series ; and still more 
o undantly in the Tertiary lacustrine deposits ; 
Oh these appear to have lived and died, under 
circumstances analogous to those which attend 
their cognate species in the lakes and rivers of 
the present tropics. They have also been found 
Plate 25', Fig. 4, represents a Turtle from the slate of 
eaul'*' ‘tie unequal elon- 
Tortol I"®® ’ t^ecause, in freshwater 
and in f ’ of moderate length ; 
in all ‘tiey are also nearly equal, and short ; but 
the a ^ h'® ®®''tral toe of 
an '’y »>’'ch the longest of all. The accord- 
nce with this latter condition in the specimen before us, is at 
once apparent; and both in this respect and in general structure 
t approaches very nearly to living genera. This figure is copied 
froni Vol. 5 Pt 2, Tab. 14,/. 4, of the Oss. Foss, of Cuvier. 
. . Agassiz has favoured me with the following details respecting 
froL R r^n represented in the drawing 
evident engraving was taken. “ The ribs show 
and S I connected with the genera Chelonia 
the Ipff referrible to no known species ; the fingers of 
shorte t °re paddle are five in number; the two exterior are the 
ternal^fi articulations; and the three in- 
each f rrhich the middle one is the longest, have 
Spharc^r as in the existing genera, Chelonia and 
G. 
S 
