The Columella Auris in Amphibia. 623 



16. The proton of the Columella is connected by a distinct strand 

 of cells with a group of cells between Squamosum, Processus oticus 

 palatoquadrati and the Prominentia semicircularis lateralis of the 

 otic capsule. 



17. The facial nerve is entirely below the Columella (stilus colum- 

 ellse) in all forms except ^Tectums, Proteus, Typhlomolge; in these, 

 one ramus (R jugularis) passes above the stilus. 



18. The relation of the stilus to the blood vessels of the otic region 

 appears quite characteristic; i. e., below the vein and above the 

 artery. 



19. A Ligamentum hyo-columellare is present in Siren, Amphi- 

 uma, Cryptobranchus, Desmognathus and many Plethodontidae. 



20. The hyomandibular homology is favorably discussed. 



21. The homology of the Columella of Urodela and the Pars 

 interna plectri of Anura is accepted. 



22. The Operculum is regarded as a secondary development in 

 those forms which possess it. 



23. From the standpoint of functional adaptation, there seem to 

 be in the Urodela three types of communication of the internal ear 

 with the exterior: (a) through the floor of the mouth, mandible, sus- 

 pensorium and columella ; (b) through the floor of the mouth, the 

 hyoid arch and columella ; (c) through the manus, pectoral girdle, 

 M. opercularis and operculum. 



24. Type (a) is the more usual and is found in typically aquatic 

 forms. Type (b) is best represented in Siren. Type (c) occurs in 

 Salamandra, Triton and Diemictylus. A combination of (a), (b), 

 and (c) is found in the Plethodontidse and Desmognathidse. 



25. There appears a close correlation of the type present and the 

 habits of the form (aquatic, semi-aquatic, terrestrial, burrowing, 

 etc.). 



Cornell University, 

 Ithaca, N. Y., June 22, 1909. 



