256 FOSSIL TESTUDINATA. 
case the shield affords compensation for the 
want of rapidity of motion to animals that have 
no ready means of escape by flight or conceal- 
ment from their enemies. We learn from Geo- 
logy that this Order began to exist nearly at the 
same time with the Order of Sanrians, and has 
continued coextensively with them through the 
secondary and tertiary formations, unto the pre- 
sent time : their fossil remains present also the 
same threefold divisions that exist among mo- 
dern Testudinata, into groups respectively adap- 
ted to live in salt and fresh water, and upon the 
land. 
Animals of this Order have yet been found 
only in strata more recent than the carboniferous 
series.*' The earliest example recorded by Cu- 
vier, (Oss. Foss. Vol. 5, Pt. 2, p. 525), is that of a 
very large species of Sea Turtle, the shell of 
which was eight feet long, occurring in the Mus- 
chelkalk at Luneville. Another marine species 
has been found at Glaris, in slate referrible to 
the lower cretaceous formation. A third occurs 
in the upper cretaceous freestone at Maestricht. 
All these are associated with the remains of other 
animals that are marine; and though they differ 
both from living Turtles and from one another, 
they still exhibit such general accordance in 
* The fragment from the Caithness slate, engraved in the Geol. 
Trans. Lond. V. iii. PL 16, Fig. 6, as portions of a trionyx, is 
pronounced by M. Agassiz to be part of a fish. 
