- 
of Fossil Footmarks. 281 
The original of the plate is extremely shallow, the clay 4 
much indurated at the time when the impression of the 
was given. This we know by the flattening of the phalangeal 
. protuberances, and because the points only of the claws are 
to be traced. This is a splendid example of these speaking 
inscriptions of past times. The class represented by it em- 
braces examples from three inches, and, I believe, less than 
that, to fourteen inches in length. I presented a specithen: of 
the latter measure to Dr. Mantell, of England, the joints of 
which were thoroughly flattened by the resistance of the stif- 
ned mud to the enornious pressure. Its middle toe was 
eight and one half inches in length exclusive of the claw, and 
its geometrical figure was identical with the central toe of the 
plate. I have a large slab in my collection, transversed by 
five individuals, whose feet present a remarkable difference in 
size, but are conformable in all. other respects. There is one 
peculiarity that characterizes this species, which, is the slight 
divergence of the toes; these members lying in contact, simply 
ing up an attenuated ridge of mud between them. Another 
peculiarity forms a contrast to this feature, and it is the di- 
vergence of the claws of the lateral toes, which point outward 
àt a great angle, while the toes are arranged in parallel order 
nearly - lam sure that the flatness of the joints is caused by the 
resistance of an unyielding medium. This prominent species 
i5 widely distributed through the layers, its great physical 
Powers sustaining it through a great proportion of the period 
9f the sandstone deposition. ! 
It will be understood by these remarks how difficult it is to 
arrange many of the footprints by specific nomenclature.’ The 
sustaining affinities to the foregoing species and to 
y others, are great, and I have ever hesitated to apply 
*Pecific names to such examples as I have discovered or de- 
dr the footprints were collected into families or 
Stoups, according to their affinities, and represented by elabo- 
‘ate drawings, it would constitute a feasible method of con- 
"eying ideas of the diversity; elegance and beauty of these 
VOL. y, 19 
