GENERA OF THE ARCIFEROUS ANURA. 105 



There are some approximations to Coecilia in AmphiamiJa\ It does not appear to 

 have been noticed that the hitter possess minute scales; the free margin of the 

 frontal seems to foreshadow the overroofiug of the orbit and temporal fossa seen in 

 Coecilia. There is also a very large foramen or canal passing through the o. maxil- 

 lare from near its middle to the orbit, foreshadowing the canalls tentaculiferus of 

 Coecilia : a narrow one occurs in the same situation in Protonopsis. Further, the 

 prominent horizontal anterior inferior processes of the vertebral centra are the same 

 in Amphiuma and Coecilia. 



B. No anterior axial cranial bone ; teeth on anterior margin of o. o. palatina. 



II. Prefrontals and pterygoids present. 



Parietals and prefrontals pi'olonged, meeting and embracing frontals. 



Orbitosphenoid separated from prootic by membranous wall. 



Wall of vestibule membranous internally. 



Premaxillaries separated. 



Carpus and tarsuscartilaginous. 



Vertebrte biconcave. 



Occipital condyles sessile. 



Protonopsid^. — Genera Protonopsis, Megalobatrachus ; Nearctic and Pala^arctic. 



C. No anterior axial bone ; palatines not prolonged over parasphenoid bearing 

 teeth on the posterior portion. No postorbital arch. 



III. Prefrontals and pterygoids present. 



Parietals and prefrontals prolonged, meeting, embracing frontals. 

 OrbitosjDheuoid sejjarated from pro tic by membranous wall. 

 Wall of vestibule osseous. 



Premaxillaries distinct, usually not embracing a fontanelle. 

 No dentigei'ous plates on the parasphenoid. 

 Carpus and tarsus osseous. 

 Vertebrae amphicoelian (biconcave.) 

 Occipital condyles sessile. 



Amblystomid^. — Genera, Amblystoma, Ensatina, and Onychodactylus. North 

 America ; one species in Japan. 



IV. Prefrontals present, pterygoids wanting. % 



Prefrontals not prolonged or embracing frontals ; parietals slightly embracing. 



Orbitosphenoids separated by membrane from prootic. 



Vestibule, inner wall osseous. 



Premaxillaries always embracing a fontanelle. 



Dentigerous plates on the parasphenoid. 



27 



