584 



B. F. Kingsbury and H. D. Reed. 



the Plethodontidge, due possibly to an early fusion of the columellar 

 blastema in front only, such a division of the plate does not occur. 

 It seems quite possible that a comparative study of the primitive 

 fenestra in urodeles might afford some evidence of this view. What 

 bearing this interpretation might have upon the periotic origin of 

 the operculum is evident. 



Desmognathidae. 

 Desmognathus fusca. In this species, the only member of the 

 small family examined, the ''sound-transmitting" apparatus mark- 



L. 8C. 





#^^ stb. 7 /^ vii 



Fig. 13. Desmognathus fusca, larva 26 mm. long. C, arteria carotis in- 

 terna ; R., ceratohyale ; L.h-c, ligamentum hyo-columellare ; L.s-c, ligamentum 

 s(|uamoso-columellare ; Sp., os squamosum; St.C, stilus columellre; V.p-l, 

 vena petroso-lateralis ; VII., nervus facialis. 



edly resembles in its general structure and relations that of the Ple- 

 thodontidse just described. In fact, they are of the same type. A 

 bony plate with cartilaginous border fits into the fenestra and pro- 

 jects caudad upon the outer wall of the recessus perilymphaticus. 

 The caudal portion is concave externally, and in the depression there 

 is inserted the M. opercularis. The cephalo-ventral border is con- 

 tinuous with the cartilaginous border of the fenestra. The stilus is 

 osseous with a cartilaginous core, the distal portion being of carti- 

 lage alone. Two figures of an adult, one (Fig. 15) through the cau- 

 dal portion showing the concave fenestral plate and the recessus • 

 the second (Fig. 14) through the insertion of the stilus, may be 



