CLASS BATRACHIA (AMPHIBIA). 



Orders. 



1. Stegocephalia. 



2. Oymnophiona. 



3. Caudata. 



4. Ecaudata. 



Sub-Orders. 



1. Branchiosauria. 



2. Aistopoda. 



3. Microsauria. 



4. Labyrinthodontia. 



ORDER 1. STEGOCEPHALIA. 



The earliest vertebrates shown by the arrangement of the 

 nares to have breathed by means of lungs at least in the adult 

 state, exhibit many resemblances to the Palaeozoic Crossoptery- 

 gian fishes in the dentition and the outward aspect of the 

 skull. They agree with these fishes much more closely than 

 with the contemporaneous Dipnoans. The conical teeth in 

 many genera exhibit a complex infolding of their wall, such 

 as is paralleled among fishes only in certain Palaeozoic genera 

 of Crossopterygians (e.g., Holoptychius, fig. 54, p. 70) ; enlarged 

 vomerine teeth like those often met with in these fishes, also 

 occur. The ring of small sclerotic plates is only paralleled 

 among fishes, so far as known, in the Crossopterygian families of 

 Rhizodontidae and Coelacanthidae. The occurrence of an infra- 

 dentary plate in the complex mandible (fig. 86 c, p. 134), if 

 confirmed, would also be suggestive of the same element or 

 series of elements in these early fishes. There is always a 

 pineal foramen, arid it is noteworthy that among Palaeozoic 

 fishes this feature is only distinctly exhibited by certain 

 Crossopterygians such as Diplopterus and Osteolepis (fig. 59, 



