(15.9 



South Africa, and in the Triassic of Europe, America, South Africa, 

 India and Australia. This shows the formerly very extensive distri- 

 bution of the Stegocephali. Some of the remains were so perfect, 

 that it was possible to study all parts of the skeleton very carefully. 

 Of Branchiosaurus from the Permian of Saxony we have complete 

 series from specimens from 30 to 120 mm in length, enabling Prof. 

 Credner to study the development of this form.^ 



The Stegocephali are vertebrates, with gills in the young stages 

 and lungs in the adult, and are therefore placed among the Batrachia. 

 The skull was completely roofed over by numerous dermal bones, only 

 leaving five openings, the two nasals, the two orbits and the pineal 

 foramen. It is totally different from that of the living Batrachia and 

 in its structure it is intermediate between the fishes and the oldest 

 reptiha. The Stegocephali show very considerable modifications. 

 Generally there are two pairs of limbs developed like those of the 

 urodelous Batrachia, but we find entirely limbless forms as early as 

 the Carboniferous. In size they vary from 10 centimetres to several 

 meters, with the skull about 1 meter long. The larger Stegocephali 

 were carnivorous, feeding mostly on fishes, as is prooved by the 

 coprolithes, which contain scales of the contemporaneous fishes. 



We may now consider some of the most important points of the 

 morphology of these animals. 



The skull. 



The skull is completely covered by dermal bones, which nearly 

 all are free from the chondrocranium, leaving, as already stated, only 

 five openings: the orbits, the nasal openings, and the pineal foramen. 

 All bones of the roof are in pairs. We have the premaxillaries, nasals, 

 lacrimals, prefrontals, frontals, postfrontals, postorbitals, parietals, 

 squamosals, prosquamosals (supratemporals, aut.), the maxillaries, 

 jugals, quadratojugals, supraoccipital plates (supraoccipitals, aut.) and 

 paroccipital plates (epiothics, aut., os tabulare. Cope). In some forms 

 (Melanerpeton, for instance) the squamosal is divided into two ele- 

 ments by a transverse suture. The lower side of the skull is 

 characterized by the extensive parasphenoid, which separates the enor- 

 mous palatal vacuities ; besides the parasphenoid, we have the ptery- 

 goids, palatines, and vomers. In some of the skulls the canals of 

 the lateral-line-system can be traced on the bones, a point, as we 

 shall see later, of very great importance for, the determination of the 

 homologies of the bones with those of fishes. 



It is well known that the dermal elements in the skull of fishes 



