EXTINCT AMPHIBIA. 



507 



pass through a metamorphosis, and become air-breathers." The chief 

 characters are the two occipital condyles to the skull, the absence of 

 sternal ribs, and the naked skin. The group as known at the pre- 

 sent day includes three sections first Saurobactrachia or Urodela, 

 which comprises the Proteidea and Salamandridea ; secondly, the 

 Gymnophiona, which includes the Caeciliidse ; and thirdly, the 

 Anura, which comprises frogs, toads, and their allies. The extinct 

 Labyrinthodontia have the external skeleton much developed, especi- 

 ally on the ventral side of the body. Professor Cope has united the 

 Labyrinthodontia with the Ganocephala and Microsauria in one group, 

 which he names Stegocephali. "With one or two exceptions the fossil 

 types belong to this group, and are found between the Carboniferous 

 rocks and the Trias. Among the Carboniferous genera l in Europe are 

 Anthracosaurus, Loxoma, Bratrachiderpeton, Pteroplax, P holiday aster, 

 Ichthyerpeton, Pholiderpeton, Lepterpeton, Urocordylus, Erprtocephalus, 

 Keraterpeton, Megalerpeton, Ophiderpeton, Dolicosoma ; Protriton and 

 Pleuronura are found in France. Archcegosaurus is common in Ger- 

 many. In North America these organisms are as well developed. In 

 Nova Scotia Den<lrerpeton,Hylonom us, Hylerpeton,J3aphetes, andJiWm- 

 rus occur, and in the coal-field of Ohio Amphibamus, Brachydectes, 

 Eupdor, Eiinithorax, &c. Several of these types range to the Permian, 

 from which Fritsch 2 has described a large fauna in Bohemia. It in- 

 cludes the genera Branchiosaurus, Sparodus, Hylonomus, Dawsonia, 

 Melanerpeton, J)olichosoma, Ophiderpeton, Palceosiren, Adenoderma, 

 Urocordi/lus, Keraterpeton, Limnerpeton, Hyloplesion, Seeleya, Ricno- 

 don, Orthocosta, Microbrackis, &c. 



Fig. 141. Branchiosaurus salamandroides (Fritsch),3 twice the natural size. 



Dr. Fritsch describes Branchiosaurus as resembling the Earth- 



1 See C. L. Miall : Rep. Brit. Assoc. 1873, 1874. 



2 "Fauna der Gaskohle, und der Kalksteine, der Permformation Bohmens." 

 Prague. 



3 From Fritsch's "Fauna der Gaskohle," &c. Prag. 1879. Electrotypes of the 

 specimens figured have been published. 



