AMPHIBIA. 311 



Limnerpeton, Melanerpeton), in which the peculiar labyrinthine in- 

 folding' of the teeth, distinctive of the true labyrinthodonts, is 

 largely absent. The apodal and ccecilian-like division Aistopoda 

 is represented among other forms by the Carboniferous genera 

 Dolichosoma and Ophiderpeton, and by Palseosiren and the Ameri- 

 can Molgophis. Contemporaneously with these types we have also 

 the true labyrinthodonts, whose earliest member appears to be 

 Baphetes, from the Carboniferous deposits of Pictou, Nova Scotia. 

 The full development of this group does not obtain, however, be- 

 fore the Triassic period, at the close of which the entire order of 

 animals seems to have become extinct in most regions.* Among 

 the more distinctive genera of this period are Labyrinthodon, Mas- 

 todonsaurus, Trematosaurus, and Metopias, to one or several of 

 which probably belong the foot-prints of the fanciful animal desig- 

 nated Cheirotherium. 



Of the perennibranchiate division of the Urodela, in which ex- 

 ternal gills are retained throughout the entire existence of the 

 animal (Siren, Proteus), we have as yet no positive indications in 

 any of the rock-formations. The Cryptobranchia, which retain a 

 gill-opening after the absorption of the gills the American Am- 

 phiuma and Menopoma, and the giant salamander of Japan, Cryp- 

 tobranchus Japonicus seem to have one or more fossil representa- 

 tives in the genus Andrias (Cryptobranchus of some authors), from 

 the Miocene deposits of Oeningen, Germany, to which are referred 

 the remains presumed by Scheuchzer to be those of earliest man 

 (Homo diluvii testis). It is certainly a very remarkable fact in dis- 

 tribution that the only link uniting the so widely separated, but 

 closely related, genera Menopoma and Cryptobranchus, should be 

 this extraordinary form from the middle Tertiary period. Its ex- 

 istence would seem to indicate a former much broader diffusion of 

 this particular group of animals, and a very different distribution 

 of land and water areas than now obtains. The caducibranchiate 

 urodeles (salamanders, tritons), which in their transformation to lung- 



* Brachyops, from the Damuda beds of India, and one or two other genera 

 of labyrinthodonts have been indicated as belonging to the Jurassic period, 

 but it may be questioned whether the age of the deposits in which these 

 remains occur has been as yet satisfactorily determined. Excepting these 

 somewhat doubtfully placed forms, no amphibians are known from Jurassic 

 strata. 



