The Columella Auris in Ampliibia. 585 



directly compared with the sections through the same regions in 

 the plethodontid, Gyrinophilus fPl. VT, Figs. 46 and 47). Similar 

 comparison may be made with Spelerpes (Figs. 6 and 7). 



The relations of the stilus to the squamosum, quadrate, facial 

 nerve, artery and vein, have been described in some detail by Kings- 

 bury ('03, pp. 321-325) for larva and adult, two sizes of each, and 

 as our investigations have not added significant details, it will be 

 sufficient to state in confirmation of the description there given that 

 while in the larva the stilus is most closely joined to the ventral 

 edge of the squamosum (Fig. 13) ; in the adult it becomes shifted 

 so as to articulate closely with the os quadratum, less closely with the 

 cartilaginous process of the palatoquadrate. The relation to artery, 

 vein and nerve is that typical of the majority of urodeles. 



Fig. 14. Desmognathus fusca, adult. Col., columella ; C.p., cavuni peri- 

 lymphaticum ; Sq., os squamosum ; St.C, stilus columelhie. 



An examination of young larvae and embryos which would deter- 

 mine the origin or origins of the stilus and fenestra! plate, has not 

 been undertaken. The mode of insertion of the stilus upon the 

 fenestral plate, as shown in Fig, 14 (compare also PI. VI, Fig. 46, 

 Gyrinophilus), might suggest that the stilus alone developed outside 

 the otic capsule, as the description of Parker would indicate. Since 

 the columella in Desmognathus doubtless develops in essentially the 

 same manner as in the Plethodontidse (Spelerpes, Plethodon) refer- 

 ence may be made to the description of its development in that 

 family, as given on p. 580. 



