448 DUNN. 



retardatus this fontanelle is absent in Hynobius and in the Crypto- 

 branehidae. 



The prevomers of Hynobius, Paehypalaminus, and Onychodaetylus 

 are broadly in contact on the median line, and extend to a greater or 

 less extent posteriorly. The dentition consists of a short outer 

 branch, curving forward and in, and a longer inner branch extending 

 backward and inward. 



The length of this inner branch depends upon the length of the 

 prevomer. Both bone and tooth row are shortest in Onychodaetylus. 

 In Batrachuperus, where the prevomers do not meet on the median 

 line, the inner branch is absent, and apparently the same condition 

 is found in Ranodon. 



Both columella and operculum are present and free in Hynobius 

 leechii. The Cryptobranehidae, and probably Ranodon and Onycho- 

 daetylus as well, lack the operculum. 



The hyobranchial apparatus of the family agrees with that of the 

 Cryptobranehidae in having the ceratobranchial and epibranchial of 

 the first arch fused into a cartilaginous rod, and in having the cerato- 

 branchial and epibranchial of the second arch present and free. The 

 Salamandroidea {Ambystomidae, Salamandridae, and Plethodontidae), 

 have the elements of the first arch usually separate, and always lack 

 the epibranchial of the second arch. 



No family characters have yet been observed in vertebrae of sala- 

 manders but I think it worth while to mention the complete agree- 

 ment of vertebrae of Cryptobranehus, Onychodaetylus, and Hynobius, 

 and the fact that no such agreement is found on comparison with 

 vertebrae of Ambystoma, of Triturus, or of Dcsmognathus. 



The ribs of Hynobius, of Onyehodactylus, and of Cryptobranchus are 

 widened proximally, but are not forked. Ribs of Salamandroidea 

 are forked. 



The number of costal grooves varies from eleven to fifteen, thirteen 

 being the usual number. Individual variation in number amounts 

 to two or three costal grooves. 



Occasional specimens of Ranodon and of some Hynobius have a 

 lateral fold of skin between the insertions of the legs, such as is very 

 prominent in the Cryptobranehidae. 



The legs are always well developed. The appressed toes may over- 

 lap along the sides, or be separated by as many as four costal folds. 

 This varies individually, as well as with age and sex. Young have 

 proportionately longer legs than adults as determined by this criterion. 

 Among the adults the males have longer legs than the females. 



