464 



ZOOLOGY. 



in the Jurassic beds of Wyoming, and two species have been 

 found in still older beds in Illinois, regarded by Cope as 

 either Upper Carboniferous or Permian. Thus, as remarked 

 by Giintber, we have in Ceratodus a genus which has sur- 

 vived from, the Triassic period.* 



The lung-fish are distinguished by two well-formed lungs, 

 and the narrow ribbon-like fins. In Lepidosiren paradoxa 

 Fitzinger, there are five gill-arches, with four slits, and the 

 body is rather longer, more eel-like, with a blunter snout 

 than in Protopterus. It grows to one metre in length, and 



Fig. 422. Skeleton of Protnpterus annectens, showing the protoccrcal tail and the 

 simple rod-like limbs, the pelvic and shoulder girdles, and the nature of the jaws. 

 ch. notochord ; p, bones representing the haemal arche- attached to the notochordal 

 sheath ; hs, hsemal spines ; in, ifi, rays of the caudal fin. After Owi-n. 



inhabits the rivers of Brazil. This is represented in Africa 

 by the closely allied Protopterus annectens Owen (Figs. 421 

 and 422 skeleton), which has six gill-arches, with three 

 pairs of external gills in the young. It is 40-70 centimetres 

 in length. It livea on leaves in the "White Nile, Q.uilimani, 

 Niger, Gambia, and their tributaries. It buries itself in the 

 mud a. foot deep. 



CLASS VI. BATEACHIA (Salamanders, Toads, and Frogs}. 



General Characters of Batrachians. We have had an- 

 ticipations of the Batrachians or Amphibia in the Ganoids, 

 especially the Dipnoan fishes, which it will be remembered 

 approach the members of the present class in the lung-like 

 nature of the air-bladder and in the presence of external 



* Description of Ceratodus, Phil. Trans. Roy. Soc., London, 1871. 

 Ayer's Beitrage zur Anatomic u. Pbys. der DipnoeT. Jena, 1885. 



