154 THE ANATOMY OF YERTEBRATED ANIMALS. 



quadrate bone is often developed. But the quadrato-jugals 

 (and even the maxillae) may be represented simply by more or 

 less ligamentous fibrous tissue, as is the case in the Urodela. 

 Pterygoid bones are developed in all Amphibia, and distinct 

 palatine bones in most, but not all, of the Batrachia. The 

 suspensorium, which is inclined downward and forward in the 

 lower Urodela, passes almost directly downward, or a little 

 backward, in the higher, and in the Batrachia slopes greatly 

 backward ; and it undergoes the same modifications in direc- 

 tion, during the progress of any of the Batrachia from the 

 larval to the adult state. 



In the mandible, the proximal end of Meckel's cartilage is 

 rarely, if ever, completely converted into a bony, articular ele- 

 ment, but the distal moiety is ossified in some Batrachia. 

 The membrane-bones of the 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 

 stout and well ossified in the Proteidea. In the Batrachia 

 they are slender, and their proximal ends may be free. Dis- 

 tally, they are connected with a broad lamellar body, from the 

 posterior margin of which two processes which embrace the 

 'arynx are usually given off. In the perennibranchiate Pro- 

 teidea, the hyoidean arches are united by narrow median en- 

 toglossal and urohyal pieces, as in Fishes. 



In the Batrachia, the branchial arches disappear in the 

 adult ; but in the Qymnophiona 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 ossified, pieces 

 on each side. In the Salaniandridea, there are, primitively, 

 four branchial arches, but of these, portions of only the two 

 anterior remain in the adult. Four are developed in the 

 Gascilia, and three of these are permanent. 



Some peculiarities exhibited by the skulls of the Crymno- 

 phiona, and by the Labyrinthodonta, are worthy of especial 

 notice. 



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

 covered b}' a complete bony roof, formed, mainly, by the ex- 

 oocipitals, parietals, frontals, prefrontals, nasals, and ascending 

 processes of the premaxillaries. 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 



