SOUND-TRANSMITTING APPARATUS OF CAUDATA 371 



The Amphiumidae have been variously placed with regard to 

 their kinship. Cope held tenaciously to the view that they rep- 

 resent a group intermediate between urodeles and the Apoda. 

 The cousins Sarasin ('87 to '90) proceed a step further, and in- 

 clude the Amphiumidae among the Apoda. Kingsley ('02) made 

 a critical study of the various supposed similarities of these 

 groups and observes that it "would appear that some of them 

 [resemblances] are of minor value, some are based upon imperfect 

 knowledge or misconception, while some are false." Kingsley's 

 study seems to have settled for all time the urodele affinities of 

 the Amphiumidae. With that much granted, the sound-trans- 

 mitting apparatus evinces an alliance with the plethodontid le- 

 gion, because of the single compound fenestral plate and the pro- 

 nounced isthmus fenestralis. Since the columella enters into the 

 formation of the fenestral plate to a lesser degree than in the 

 Necturidae, they must be considered an offshoot of the pletho- 

 dontid stem, between the Necturidae and those still more spe- 

 cialized with regard to this feature. Furthermore, the greater 

 reduction of the columellar element as a component of the fen- 

 estral plate in the Amphiumidae bespeaks a longer terrestrial 

 period for this family than probably existed in the case of the 

 Necturidae. 



The Typhlomolgidae are unquestionably of the plethodontid 

 legion, as indicated by the absence of lungs and by their similar- 

 ity to Spelerpes larvae in most of their structural peculiarities, 

 as pointed out by Emerson ('05) in her study of the anatomy of 

 Typhlomolge. The sound-transmitting apparatus is decidedly of 

 the plethodontid type, with a still smaller amount of the colu- 

 mella entering into the fenestral plate than in the Amphiumidae. 

 Emerson expresses the opinion that the Typhlomolgidae should 

 be included with the Plethodontidae. So far as the morphology- 

 of the sound-transmitting apparatus can be made out from the 

 adult alone, it does not warrant such a union of families. A 

 noticeable amount of the columella contributes to the plate part 

 of the apparatus, which is not the case in any of the Plethodont- 

 idae. While not to be included with the Plethodontidae, Typh- 

 lomolge appears to have been derived in very close relations with 

 them. 



