The Columella Auris in Amphibia. 



607 



Plethodon, Stereochilus, Autodax, Manculus (Batracoseps). The 

 Desmognathidse (Desmognathiis fusca.) 



Two forms are exceptional; Batracoseps, which otherwise falls 

 under group VII, possesses a vestigial stilus and therefore lacks the 

 connection with the suspensorium, usually well developed in the 

 Plethodontidse. The interesting form Typhlomolge is plethodontid 

 in the character of the fenestral plate, but possesses a fragmented 

 stilus. The interesting course of the R. jug. VII over the stilus, 

 and the absence of the M. opercularis, however, places it in Group I. 



Briefly classified from the point of view of the existence of two 

 fenestral structures, Columella and Operculum, these forms may be 

 divided into the following groups : A, groups I and II ; the columella 

 present, free, connected with the suspensorium, no operculum or 

 opercular muscle. B, groups III and IV; the columella present, 

 fused with the otic capsule, connected with the suspensorium, oper- 

 culum and opercular muscle present. C, group V; columella ves- 

 tigial, fused with the ear capsule, no connection with the suspensor- 



