THE FIRST AIR-BREATHERS. 



155 



been species of this type much larger than any represented by 

 skeletons, and with bodies perhaps six inches in diameter. It 

 is not unlikely that they had the habits of the modern water- 

 snakes. 



A second line leads upward to large crocodile-like creatures, 

 with formidable teeth, strong bony armour, and well-developed 

 limbs {Labyrmthodontia, Figs. 136, 137). Some of them must 

 have attained a length of ten feet. They were lizard-like in 

 form, could walk well, as is seen from the footprints of some 

 of the species which present a considerable stride, and moved 



Fic. 136. — A large Carboniferous Labyrinthodont {Bajihetes plnniceps, Owen). 



a. Anterior part of the skull, viewed from beneath. One-sixth natural size, b. One of 



the largest teeth, natural size. 



over mud without the belly touching the ground. Their tails 

 were long, and probably useful in swimming. Their heads 

 were flat and massive, and their teeth were strengthened by a 

 remarkable folding inward of the outer plate of enamel 

 (Fig. 137 h). The belly was protected by bony plates and 

 closely imbricated scales. In some of the species at least the 

 upper parts were clothed with horny scales, and the throat and 

 sides were ornamented with pendant scaly fringes or lappets. 

 Their general aspect and mode of life must have resembled 



^ There are known in some of the smaller species, but not as yet in the 

 larger. 



