8o 



STEGOCEPHALI 



CHAP. 



articulars, angulars, and splenials. The dentaries and apparently 

 sometimes the splenials, the palatines, maxillae, and vomers carry 

 teeth. The eyes possess a ring of sclerotic bones. 



Order I. STEGOCEPHALI LEPOSPONDYLI. 



Vertebrae pseudocentrous. 



Sub-Order 1. Branchiosauri. The young had several pairs 

 of gill-arches, which, to judge from their size and from the 



FIG. 12. A, Dorsal and B, ventral views of the cranium of Branchiosaurus salaman- 

 droides, x about 4. (After Fritsch.) C, Posterior view of the cranium of Trewato- 

 saurus, x about . (After Fraas.) Br, Branchial arches ; C, condyle ; Ep, epiotic ; 

 F, frontal ; J, jugal ; L. 0, lateral occipital ; M, maxillary ; N, nasal ; A\>, nostril ; 

 Pa, parietal ; PI, palatine ; Pm, premaxillary ; P.o, postorbital ; Pr.f, prefrontal ; 

 Ps, parasphenoid ; Pt, pterygoid ; Ptf, postfrontal ; Q, quadrate ; Qj, quadrato-jugal ; 

 S.o, supraoccipital ; 8q, squamosal ; St, supratemporal ; V, vomer. 



fact that they are beset with numerous nodules, denticles, or 

 irregular little processes like gill-rakers seem to have been 

 exposed to the surface and to have carried gills. In the adult 

 the arches and gills seem to be absent. 



One of the commonest genera is Branchiosaurw, including 

 Protriton. B. salamandroides of the Lower Bed Sandstone of 

 Europe is known in every stage, from larvae of 16 mm. to the 

 full grown animal of 64 mm. in length. The whole body was 



