The eighth group is assigned by President Hitchcock to the Chelonian
or turtle tribe. The slab bearing impressions of Brontozoum
Gracillimum has a mark about fourteen inches long and two wide, which
may be attributed to the plastron or breast-plate of the tortoise. On
the slab from Turner's Falls there is a longitudinal furrow, which
might have been made by the tail of a turtle; and in various of our
slabs are impressions which we think belong to this tribe. We shall
have occasion to notice hereafter remarkable tracks of these animals
in the old red of Morayshire, in Scotland.
The most distinct of the traces of chelonians are on the large slab
lately obtained for me by President Hitchcock from Greenfield. (_Vide_
Plate.) This interesting slab contains the traces of quadrupeds,
various birds, and two trails of chelonians: the largest of these is
nearly five feet long, and four inches in diameter. The trail is
composed of a number of parallel elevations, comparatively
superficial.
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