552 B. F. Kingsbury and H. D. Keed. 



becomes fused with the ear capsule at transformation when an oper- 

 culum is formed. A further reduction and fusion of the columella 

 is encountered in Salamandra, Triton and Diemictylus (Salaman- 

 dridse and Pleurodelidse, Cope). In the Plethodontidse and Des- 

 mognathidse the fenestral plate of the columella embodies a repre- 

 sentative of the operculum which is not separately developed. 



7. The hyomandibular homology of the Columella is strengthened. 



How widely the results of a detailed examination of a large 

 number of forms depart from the interpretations at present accepted 

 based upon the available information as to the morphology in a more 

 limited number of salamanders, may be seen from a comparison of 

 the above with the statements in two of the standard works: The 

 Comparative Anatomy of Vertebrates, by Dr. Robert Wiedersheim, 

 and the section upon the development of the skull, by Dr. Ernst 

 Gaupp, in Hertwig's Handbuch der Entwickelungsgeschichte der 

 Wirbeltiere. 



The former ('06) describes" the fenestra vestibuli as filled by a 

 cartilaginous plate, the so-called Stapedial plate or Operculum which 

 is joined to the Palatoquadrate and Paraquadrate (squamosum) by 

 ligaments, cartilage or bone. This bridge between the stapedial plate 

 and the quadrate (or paraquadrate) is called Columella and together 

 with the Operculum., in a phylogenetic sense, corresponds with the 

 proximal segment of the hyoid arch (hyomandibulare or possibly 

 symplecticum) . Ontogenetically such a relation does not occur, both 

 operculum and columella arising by differentiation in the territory 

 of the otic capsule. 



Professor Gaupp ('05) in Hertwig's Handbuch (pp. 696, 697, 

 605) designates the entire "stapedial" element as Columella auris, 



^"Sie [Fenestra ovalis] wird von einem durch Bandmassen oder auch durch 

 Knorpel oder Knochen an das Quadratum iind Paraquadratum befestigten 

 Knorpeldeckel, der sog, Stapesplatte (St) oder dem Operculum, verschlossen 

 und soil uns bei der Anatomie des Gelior-Organs wieder beschaftigen. Jene 

 zwischen Stapesplatte und Quadratum resp. Paraquadratum sich erstreckende 

 Briicke heisst Columella und entspricht zusamt dem Opercukmi in phylo- 

 genetischer Beziehung dem oberen Abschnitt des Hyoidhogens. Ontogenetisch 

 ist von diesen Beziehungen nichts mehr uacbzuweisen, sondern es bande't 

 sich sowohl fiir die Columella als fiir das Operculum hinsichtlich ihrer 

 Entstehung um Differenzierungsprocesse im Bereich der Labyrinthkapsel." 



