424 THE AMERICAN NATURALIST [Vol. LVI 



mountain brook habitat of the ancestral Plethodontid 

 (Wilder and Dunn, 1920) accounts perfectly for the re- 

 tention of the columella through adult life as a working 

 part of the sound-transmitting apparatus. 



The Cryptohranchoidea contains two families. Of 

 these the Hynohiidm is the more primitive. The Crypto- 

 branchidce differ in lacking the lachrymal bone, in the 

 larval position of the vomerine teeth, and in the much 

 depressed form of the body and head, the last two evi- 

 dently adaptations for aquatic and bottom-living habits. 

 Besides the characters mentioned in the list as aligning 

 the Cryptohranchidce with the HynobiidcB, several minor 

 points also show this relationship. Both Banodon and 

 Hynohius frequently have a lateral fold between the in- 

 sertions of the legs. This is very prominent in both 

 Cryptohranchus and in Megalobatrachus, and is not 

 found elsewhere. Onychodactylus larvsB have a marked 

 fold on the posterior side of the limbs. This is seen else- 

 where only in Cryptohranchus and in Megalobatrachus. 



Inasmuch as the characters differentiating the two gen- 

 era of CryptobranchidcB have not been clearly understood 

 in the past they are here stated. 



Megalobatrachus, Two persistent branchial arches : 

 Frontal not entering naris : 

 Branchial clefts closed in adult. 



Cryptobranchus, Three persistent branchial arches: 

 Frontal entering naris : 

 Branchial clefts open in adult. 



In all three of these characters the American genus 

 shows greater adaptation to aquatic life. The European 

 fossils of this family appeal to Megalobatrachus in the 

 one skull character which separates the two genera. 

 Neither in Andrias schuchzeri nor in A. tschudii does 

 the frontal enter the naris. 



It is also interesting to note that Megalobatrachus 

 shows no "Derotreme" characters whatever, although 

 in the older classifications it was included in the Dero- 

 tremata. 



