THE BATRACHIA OF NORTH AMERICA. 121 



latter family is, therefore, between the Pletliodoutidaj and the Sala- 

 mandridie. The Amblystomidce and Plethodoudidine may be thus com- 

 pared with reference to the developmental character of the features 

 which distinfi'uish them. 



AMBLYSTOMID.E. 



Su2Jerio7'. 



Carpus and tarsus osseous. 

 Prem axillary fontanelle closed. 



Inferior. 



0. iHerijgoideum persistent. 



PLETHODONTID.E. 



Inferior. 



Carpus and tarsus cartilaginous. 

 Premasillary fontanelle opeu. 



Superior. 



0. pterygoidetim obliterated. 



The inferiority of some Plethodontid?e is seen in the non-distinction 

 of the digits (ffidipns), the thinness of the ossification of the parietal 

 membrane bones (Batrachoseps), and in (Edipina the persistence of the 

 membranous cranium by the limitation of the parietal bones to two 

 small oval lateral scales and the wide divarication of the posterior ex- 

 tremities of the frontals. 



The genera embraced in this family are as follows: 



Section I. The tongue attached from the central or posterior pedicel to the anterior 

 margin in narrower or wider band. (Plethodontte.) 

 A. Two premaxillary bones. 



Digits 4,5; maxillary bone regular, with numerous small teeth; parietals 



fully ossified Flethodon. 



Digits 4, 4 ; maxillary as above, parietals fully ossified HemidacUjlium. 



AA. One premaxillary. 

 a. Digits 4, 4. 



Maxillary regular, with small teeth ; parietals not ossified . . - Batrachoseps. 

 aa . Digits 4, 5, 



Maxillary normal ; teeth small, very numerous ; no premaxillary fonta- 

 nelle SiereocliiJus. 



Maxillary edentulous posteriorly, decurved, forming a cutting edge ; teeth 



few, large, knife-shaped ; a premaxillary fontanelle. Autodax. 



Section II. The tongue free all round ; attached by its central pedicel only. (Spe- 

 lerpes. ) 

 A. Two premaxillary bones (with fontanelle). 



Digits 4, 5, closely united by a broad palmar membrane Geoiriton. 



Digits 4, 5, entirely free GyrinopMlus. 



AA. One premaxillary bone (with fontanelle). 

 «. Digits 4, 4. 



Digits free ; parietal and palatine bones well ossified MancuJus. 



aa. Digits 4, 5. 



Digits all free ; cranial bones well ossified SpeJerpes. 



Digits little distinct; parietal and palatine cartilages not ossified. 



CEdipina. 



Digits entirely confounded as an undivided palm or sole ; cranial bones 



well ossified CEdipus. 



The generic relationships of the above-named groups are exceed- 

 ingly simple, and the ease with which the animals can be analyzed ren- 

 ders the case free from the doubts which constantly arise in discus- 

 sions of generic relationships as to the probable omission of characters 



