GENERA OF THE ARCIFEROUS ANURA. 105 



There are some approximations to Coecilia in Amphiuraidaj. It does not appear to 

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

 frontal seems to foreshadow the overroofing 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 canal is 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 CcEcilia. 



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



II. Prefrontals and pterygoids present. 



Parietals and prefrontals prolonged, meeting and embracing frontals. 



Orbitosphenoid separated from prootic by membranous wall. 



Wall of vestibule membranous internally. 



Premaxillaries separated. 



Carpus and tarsus cartilaginous. 



Vertebrae biconcave. 



Occipital condyles sessile. 



PROTONOPSiDiE. — Genera Protonopsis, Megalobatrachus ; Nearctic and Palsearctic. 



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

 teeth on the posterior portion. No postorbital arch. 



III. Prefrontals and pterygoids present. 



Parietals and prefrontals prolonged, meeting, embracing frontals. 

 Orbitos|)heuoid separated from pro tic by membranous wall. 

 Wall of vestibule osseous. 



Premaxillaries distinct, usually not embracing a fontanelle. 

 No dentigerous plates on the parasphenoid. 

 Carpus and tarsus osseous. 

 Vertebrse amphicoelian (biconcave.) 

 Occipital condyles sessile. 



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

 America; one species in Japan. 



IV. Prefrontals present, pterygoids wanting. 



Prefrontals not prolonged or embracing frontals ; parietals slightly emhi'acing. 



Orbitosphenoids separated by membrane from prootic. 



Vestibule, inner wall osseous. 



Premaxillaries always embracing a fontanelle. 



Dentigerous plates on the parasphenoid. 



27 



