No. 646] THE PHYLOGENY OF THE CAUDATA 



419 



culum are present as free and distinct elements. Both 

 are readily movable. There is a m. opercularis. 



I have not been able to examine skulls of Onychodac- 

 tylus, or of Ranodon. Okajima's (1908) figures of Ony- 

 chodactylus show only one element which is in appear- 

 ance much like that of CryptohrancJms. This is very 

 different from the appearance of the apparatus of Hyno- 

 bius. It is evident that either fusion of operculum and 

 columella has taken place or that the operculum has not 

 developed. OnycJiodacfyhis is partly a(iuatic. a nionn- 

 tain brook animal. Cri/ptolirtnicliH.^. wliicli. ns I slmll 

 show later, is a derivative of the fl ij)i(>hiifl(> . li.-is t'nilcd 

 to develop the operculum. Prol)ably the smihc is true 

 of OnycJiodactylus and of llanodou as well, althoug-h for 

 the latter Wiedersheini's (1877) figure is all we have. 

 Still, as Kingsbury and Reod (1009) say, his Fig. 67 

 ''suggests a condition such as is found in ( ' nipt'thnm- 

 chus?' 



Bhyacotrifou olympicus was not cxaiiiiiKMl by Kinirs- 

 bury or by Keed. This animal ( Dniin. I'.'i'n) po^M.^^os 

 both columella and ()])('ix'ulum. The (•oiuiiirihi i> t ivc t i-oin 

 the periotic and is readily movable. The (.immvuIuih is 

 little developed. The animal is in part a.iualie. a nmiin- 

 tain brook species. 



Dicamptodon ensatus was examined by Kingsbury and 

 Eeed (1909), and while my dissection of an adult showed 

 the state of affairs which they describe, I can not follow 

 them in calling it ''much like that in the adult Amby- 

 stoma.''^ In adult Amhystoma the columella is solidly 

 fused to the periotic. A bony operculum nearly fills the 

 opening of the fenestra, and is attached by a membrane 

 around its circumference. In Dicamptodon, on the other 

 hand, about half of the fenestra is filled by the plate of 

 the columella, and the remainder by cartilage. The car- 

 tilage extends around the plate of the columella. There 

 is nothing that could be called a definite operculum. If 

 the cartilage is called the operculum, then the columella 

 and operculum are fused and the operculum is fused to 



