154 



THE CHAIN OF LIFE. 



Leaving these fish-like forms, we find the remainder of the 

 carboniferous reptiles to diverge from them along three lines. 



The first leads to snake-like creatures, destitute of limbs, 

 and which must have been functionally the representatives of 



Fig. 134. — Archegcuiunis Decheni. 



Head and anterior limb reduced. Coal-field ot 

 Saarbruck. 



the serpents in the Palaeozoic, though batrachian in their 

 affinities (Fig. 135). They are found both in Europe and 

 America ; and Huxley describes one from Ireland more than 



Fig. 135. — Ptyonius. A Snake-like Amphibian. Coal-measures of Ohio. — After Cope. 



twenty-one inches long, and with over one hundred vertebrae.^ 

 Some extraordinary traces are found on the sandstones of the 

 coal-formation,^ which appear to indicate that there may have 



^ Ophiderpeton Brouinriggii. ^ Diplichnites. 



