3G 



BULLETIN 34, UNITED STATES NA.TIONAL MUSEUM. 



Tlie most primitive form of the existing Urodcla is apparently Cryp- 

 tobrancluis. 



Wiedersbciin * {I. c, p. 95) Las attempted to trace tlie ancestry of the 

 CiBciliida; to the Stegocephali of the Carbouiferoas period, from which 

 he snpposes them to have arisen by a process of degeueratiou. He re- 

 marks that in order to demonstrate this proposition it is only necessary 

 to discover a type with rudimental limbs which shall connect the two. 



That the Cneciliidie is a type which has resulted from a degeneration, 

 1 have also proposed,! but T have derived them from the Urodela rather 

 than from the Stegocephali direct. They have, like Amphiuma, essen- 

 tially the same cranial structure as the LTrodela, which is widely different 

 from that of the Stegocephali, in the absence of the intercalare, supra 

 temporal, basioccipital and i)Dstorbital bones. And these cliaracters 

 are fully maintained in various genera of Stegocephali which have rudi- 

 mental limbs. Amphiuma then is the anuectant type with rudimental 

 limbs which Dr. Wiedersheim sought for. The circumstance that his 

 eyes were turned toward the Stegocephali indisposed him to recognize 

 this fact. 



Theaflinities of the recent families, which may be regarded as phylo- 

 genetic, may be represented as follows: 



Thoriicko. 



Plethodontidai. 



CaeciliidsB. 



Aiiipliiiimid;e. 



DcsmorjuatUidii;. 



AtublystomuhB. 



Plciirodclidtc. 



Salaiiiaadridaj. 



CryptobrancliidiB. 



CRYPTO BRA NCniD^E. 



Vertebra? amphicoelous, without anterior double hypopo[)liysis. Tail 

 developed. Parietal and prefrontal bones embracing frontals, and 

 meeting above orbits. Vestibule with internal wall membranous. No 

 ethmoid bone. Carpus and tarsus cartilaginous. Yomeropalatine teeth 

 on anterior border of bone of that name. Pterygoid bone present. 



"Anatomie der Gymnophionen, Jeua, 1879. 



tAmericau Naturalist, 1885, p. 244. 



