30 ANURA CHAP. 



tympanic cavity is much reduced, for instance in Bortibinator, 

 Liopelma. In Batrachophrynus not only the cavity, but also the 

 Eustachian tubes are suppressed. In the Aglossa only the two 

 tubes are united into one short but wide median canal, opening 

 at the level of the pterygoids on the roof of the mouth. 



The lower jaw is remarkable for the possession of mento- 

 Meckelian cartilages, absent only in the Aglossa and Disco- 

 glossidae. At first they are much longer than the rest of the 

 jaw ; during the larval life they indeed form the functional 

 jaw, and they are now covered with horny sheaths instead of 

 teeth. Owing to the absence of teeth on them, these mento- 

 Meckelian cartilages are later not invested by bone, although in 

 many Anura they ultimately ossify, either retaining their sepa- 

 rate nature or fusing partly with the dentary bones. The bulk 

 of the lower jaw, the Meckelian cartilage, becomes invested by 

 the dentary, a small articular e, and an inner angulare, while a 

 splenial element is absent. The dentary itself is mostly reduced 

 to a small dentigerous splint, while the angulare forms by far 

 the greater part of the bony jaw. 



Teeth are more restricted in their occurrence than in the 

 Urodela. On the jaws they always stand in one row. With 

 the exception of the Hemiphractinae, Amphignathodontinae, 

 Ceratobatrachinae, and Genyophryninae, no recent Anura carry 

 teeth on the lower jaw, and even in these genera they are mostly 

 much reduced in size and firmness, having all the appearance of 

 vanishing structures. The premaxillae and maxillae are frequently 

 furnished with teeth, except in the Dendrobatinae, Genyophry- 

 ninae, Engystomatinae, Dendrophryniscinae, Bufonidae, Pipa, and 

 Hymenochirus. The vomers mostly carry a series of teeth on 

 their posterior border ; when these teeth are absent, as in many 

 species of Bufo, a kind of substitute sometimes occurs on the 

 palatines in the shape of a row of tuberosities. The palatines 

 carry teeth in Hemiphractinae. The parasphenoids are rarely 

 toothed, e.g. Triprion, Diaglena, Ampkodus, and occasionally in 

 Pelobates. 



A few Anura possess peculiar substitutes for teeth in the 

 anterior portion of the lower jaw, namely, a pair of conical 

 bony processes, sometimes rather long, but always covered by 

 the dense gums, or investment of the jaws ; e.g. Lepidobatrachus, 

 several Rana, e.g. R. adspersa, R. khasiana, R. kuhli, and Cryptotis 

 Irevis. 



