CARBONIFEROUS PERIOD 59 



"backbones" incompletely ossified. The under-part of the 

 body was well covered with scales, affording protection in 

 creeping over hard ground (Branchiosaurus). Others, in 

 some cases four times the length, with elongated heads, 

 tapering snouts, and long tails, possessed fairly stout hind- 

 limbs, and the string of gelatinous tissue (notochord) running 

 through the length of the body was enclosed in bony cylinders 

 (Keraterpeton, Lepterpetori). In more advanced stegocephs, 

 the vertebral column was well ossified, and had undergone 

 divisional processes in order to render it more flexible 

 (Dendrerpeton). These were strong-limbed little creatures, 

 and probably penetrated far into the sylvan solitudes. 

 Besides these, some large amphibians were abroad with 

 skulls a foot and more in length, and with jointed backbones 

 completely ossified (Loxomma, Anthracosaurus). Their teeth 

 were remarkable, as numerous folds of the coating enamel 

 invaded the dentine or inner substance of the teeth in a 

 labyrinthine manner. These animals, known as labyrintho- 

 donts, appear to have been the most formidable members of 

 the new life ; and in the absence of serious competition they 

 doubtless fared sumptuously in their watery and riverside 

 haunts. 



Then there were other forms about a yard in length 

 that had lost their limbs (Dolichosoma) ; and must have 

 somewhat resembled the limbless amphibians of our own 

 time (Apoda). They probably preyed on the fishes and 

 smaller stegocephs : and may occasionally have found them- 

 selves between the labyrinthine teeth of the lords of the 

 rivers and marshes. 



That the stegocephs were evolved from fishes there can 

 be little doubt. Even at the present time amphibians retain 

 many affinities with fishes, and Carboniferous amphibians 

 held closer relationship with the fishes of their time. Their 

 nearest relatives appear to have been the fringe-finned 

 ganoids (Crossopterygians). These they resembled in several 

 anatomical respects, notably in the structure of the skull, 

 and in the hard plates round the eyes ; whilst the labyrin- 

 thodonts the most important amphibians possessed teeth 

 much as those of some of the fringe-finned ganoids. The 



