ICHTHYOPSIDA, 255 
to be little more than mentioned. The Labyrinthodonts were 
Amphibia which were all of large size, and of which some 
must have attained absalutely gigantic dimensions, the skull 
of one species being three feet in length and two in breadth. 
They were first known to science simply by their footprints, 
which were found in certain Secondary sandstones (77zas). 
These footprints consisted of a series of alternately placed 
pairs of hand-shaped impressions, the hinder print of each pair 
being much larger than the fore one. So like were these prints 
to the shape of the human hand that the unknown animal which 
had produced them was christened the “Chezrotherium” (Gr. 
chetr, hand ; ther, beast). Further researches, however, showed 
that these footprints were produced by various species of large 
Amphibians, to which the name of Ladyrinthodontia was ap- 
plied, in consequence of the complicated microscopic structure 
of the teeth. These extinct Amphibians are known to have 
existed at the time of the Coal, but they are most characteristic 
of the period known to geologists as the Trias, 
