586 



B. F. Kingsbury and II. D. Reed, 



Desmognathus possesses a short but well developed ligamentum 

 hjo-columellare, in this respect also agreeing with many of the Ple- 

 thodentidse. In Fig. 13 it is indicated in the larva. 



Typhlomolge. 



A single adult 95 mm. long was studied by means of serial sec- 

 tions and a model of the entire skull in the otic region. The fenestra 

 vestibuli is filled by a single plate as in the Plethodontidse, connected 

 by a long and slender stilus with the suspensorium. On the cephalo- 

 ventral margin the fenestral plate is fused with the ear capsule. 



M.op 



Fig. 15. Desmognathus fusca, adult. C.p., cavum perilymphaticum ; M.( 

 musculus opercularis ; Op., operculum ; R.p., Recessus perilympliaticus. 



The stilus is relatively longer than in any of the other forms exam- 

 ined. This is probably due to the extreme flattening of the skull, 

 which has brought the long axis of the suspensorium more nearly 

 parallel with that of the skull, thus throwing the attachment of 

 the stilus to the suspensorium farther cephalad. It seems likely that 

 this flat condition of the head is the result of an adaptation to sub- 



