The Columella Auris in Amphibia. 553 



consisting of an Operculum which may or may not bear a process, 

 the Stilus columellce. The process when present is usually connected 

 by means of a ligament (Ligamentum suspensorio-columellare) with 

 the Paraquadratum, Palatoquadratum or with both. The facial 

 nerve in most forms passes below the suspensorio-columellar connec- 

 tion. It is stated, however, that there are two such connections, one 

 above and one below the facial nerve. The operculum with a stilus 

 is regarded as the more primitive condition and as such is probably 

 to be homologized with the Hyomandibulare. In the Anura the 

 Columella auris consists of two elements, Operculum and PlecU^nij 

 the latter (Pars interna plectri) probably to be interpreted as a 

 stilus which has become secondarily dissociated from the operculum. 



Nomenclature. The question of nomenclature is a perplexing one. 

 Gaupp has termed the entire fenestral structure, Columella auris, 

 consisting in Anura of two elements. Operculum and Plectrum, in 

 Urodela of Operculum and (typically) its process, Stilus Colum- 

 ellse. The direct application of the terms used by Gaupp, though 

 desirable, becomes difficult in the light of the existence of a stilus- 

 bearing fenestral plate and a non-stilus-bearing fenestral plate in the 

 same form and at the same time. While there are objections to both 

 the terms Columella and Operculum, it seemed better to avoid the 

 introduction of uew terms and to employ the term perculum for the 

 stilus-free structure and to restrict the name Columella to the stilus- 

 hearing element. This use of terms seems to necessitate less depar- 

 ture from the earlier use of the names. The operculum of Anura is 

 directly comparable with that which is termed by us operculum in 

 the Urodela. This in Siredon was termed Operculum' cartilageneum 

 by Windischmann in 1831 and subsequently has often been designated 

 Operculum in other salamanders. Columella was, of course, applied 

 to the anuran structure now named Plectrum by Gaupp, and to the 

 stilus in Urodeles, or to the entire element (Hasse, '73) called 

 columella by us. 



As an indifferent name for bony or cartilaginous plate fitting into 

 the fenestra vestibuli we employ the term fenestral plate. A back- 

 ward extension of the Cavum perilymphaticum beneath the operc- 

 ulum we designate Recessus penlympJiaticus. For the bulging por- 



