AMPHIBIA. 283 



SUB-CLASS I. STEGOCEPHALI 

 (LABYRINTHODONTIA). 



. Extinct amphibia with well-developed tail ; skull solid, with 

 numerous dermal bones, including paired supraoccipitals, supra- 

 temporals, and postorbitals ; the lower surface of the body 

 usually with three large ventral bony shields, and frequently 

 with smaller scales which may extend over the dorsal surface 

 and limbs ; a separate pubic ossification. The stegocephali ap- 

 pear in the carboniferous 1 and became extinct in the triassic. 

 Some were of gigantic size, and in some the dentine of the 

 teeth was so folded as to give these animals the name of laby- 

 rinthodonts. 



ORDER I. LEPOSPONDYLI. 



With vertebral centra consisting of bony envelopes surround- 

 ing the persistent notochord ; teeth simple, with large pulp 

 cavities. BrancJiiosaurus (one species about four feet long) had 

 persistent gills, and the ventral surface of body, limbs, and 

 tail with oval scales. European carboniferous. Melanerpeton. 

 The MICROSAURIA, with pointed heads and weak fore limbs, are 

 well represented in the carboniferous of Nova Scotia {Hylerpe- 

 ton, Hylonomns) and Ohio (Tutidanus, Colosteus}, as well as of 

 Europe (Keraterpeton). In the AISTOPODA the body was snake- 

 like and limbless. DolicJiosoma, Ophiderpeton, European car- 

 boniferous ; Phlegethontia (coal of Ohio) lacked ribs. 



ORDER II. TEMNOSPONDYLI. 



Vertebrae embolomerous or rhachitomous, dentine of teeth 

 radially folded. RHACHITOMI, with rhachitomous vertebrae. 

 Archegosaurus, the best known stegocephalan (European car- 

 boniferous), five feet long. Trimerorhachis (Texas Permian) had 

 a skull five feet long. Eryops from the same beds was half as 

 large. EMBOLOMERI, embolomerous vertebrae. Cricotus, Permian 

 of Texas and Illinois. 



1 Foot-prints, possibly of a stegocephalan, have recently been found in the Devonian 

 of Pennsylvania. 



