178 THE ANATOSIT OF VEETEBEATED ANIMALS. 



The membrane bones of tbe mandible are a dentary and 

 a splenial piece, with, perhaps, an angular element. 



The hyoidean arch is, in most Amphibia, connected with 

 the suspensorial cartilage — sometimes quite close to its 

 origin, sometimes near its distal end, in the Urodela. Its 

 cornua are stoiTt and well ossified in the Proteidea. In the 

 Batrachia they are slender, and their proximal ends may 

 be free. Distally, they are corm^ected with a broad lamellar 

 body, from the i^osterior margin of which two processes which 

 embrace the larynx are usually given off. In the peren- 

 nibranchiate Proteidea, the hyoidean arches are united by 

 naiTow median entoglossal and urohyal pieces, as in Fishes. 



In the Batrachia, the branchial arches disappear in the 

 adult; but in the Gymnophiona and in the Urodela, more 

 or fewer of the larval branchial arches persist throughout 

 life. 



In the Proteidea there are three or four branchial arches, 

 each usually consisting of two cartilaginous, or ossiiied, 

 pieces on each side. In the Salaniandridea, there are, primi- 

 tively, four branchial arches, but of these, portions of only 

 the two anterior remain in the adult. Four are developed 

 in the Ccecilia, and three of these are permanent. 



Some peculiarities exhibited by the skulls of the Ch/mno- 

 phiona, and by the Labyrinthodonta, are worthy of especial 

 notice. 



In the former, e.g. in Ichthyophis glutinosa, the skull is 

 covered by a complete bony roof, formed, mainly, by the 

 ex-occipitals, parietals, frontals, prefrontals, nasals, and as- 

 cending processes of the premaxiUaries. Between the ex- 

 occipitals, the parietal, and the frontal, above, the maxilla, 

 in front, and the quadrate, behind and below, lies a bone 

 which appears to answer to the bone («) of the Frog, and to 

 its quadrato-jngal. Between the nostril and the maxilla, 

 the nasal bone and the premaxilla, there is a bone which 

 seems to be an ossification of the cartilaginous ala nasi. 

 Another bone nearly encircles the orbit, and, as a supra- 

 and postorbital bone, has no analogue among existing 

 Amphibia. The palatine bones suiTound the posterior and 



