The genera Trionyx and Emys, present their fossil species. in the Wealden freshwater formations of the Secondary series; and still more abundantly in the Tertiary lacustrine deposites; all 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 in marine deposites, where their admixture with the remains of Crocodilean animals shows that they were probably drifted, together with them, into the sea, from land, at no great distance.[1]
In the close approximation of the generic characters of
these fossil Testudinata, of various and ancient geological
epochs, to those of the present day, we have a striking example
of the unity of design which has pervaded the construction
of animals, from the most distant periods in which
these forms of organized beings were also called into existence.
As the paddle of the Turtle has at all times been
adapted to move in the waves of the sea, so have the feet
of the Trionyx and Emys ever been constructed for a more
quiescent life in freshwater, whilst those of the Tortoise
have been no less uniformly fitted to creep and burrow
upon land.
5, Pt. 2, Tab. 14, f. 4, of the Oss. Foss: of Cuvier M. Agassiz has favoured me with the following details respecting important parts which are imperfectly represented in the drawing from which Cuvier's engraving was taken. "The ribs show evidently that it is nearly connected with the genera Chelonia and Sphargis, but referable to no known species; the fingers of the left fore paddle are five in number; the two exterior are the shortest, and have each three articulations; and the three internal fingers, of which the middle one is the longest, have each four articulations, as in the existing genera, Chelonia and Sphargis".
- ↑ Thus two large extinct species of Emys occur, together with marine shells, in the jura limestone at Soleure. The Emys also and Crocodiles, are found in the marine deposites of the London clay at Sheppy and Harwich; and the former is associated with marine exuviæ at Brussels. Very perfect impressions of small horny scales of Testudinsts, occur in the Oolite slate of Stonesfield, near Oxford.
