THE AMPHIBIAN SKULL. itt 



to the ethmoid, the anterior half of the girdle-bone to the pre- 

 frontals, or part of them, and the posterior haK of the girdle- 

 bone to the orbitosphenoids of other Vertebrata. Tnrbinal 

 ossifications are developed in the cartilage bounding the 

 nasal capsules in some Amphibia. 



The membrane bones of the Amphibian skull are : — 

 1. Frontals and parietals, which, in the BatracMa, may be 

 fused together into one bone. 2. Nasals are generally pre- 

 sent. 3. The vomers, always present, are two in number, 

 one for each side, in all Amphibia but Pipa, Dactylethra, and 

 Pelobates. 4. A great parasphenoid covers the base of the 

 skull from the occipital to the ethmoidal region, as in Teleostei 

 and Ganoidei. 5. A membrane bone (Z), called " temporo- 

 mastoid " by Duges, lies on the outer side of the suspen- 

 sorium, extending from the side-walls of the skull to the 

 articular head for the lower jaw. The relations of this 

 bone in its upper part are similar to those of the squamosal 

 of the higher Vertebrata, in its lower part to those of the 

 bone F in Lepidosiren, to the preoperculum of fishes, and 

 to the tympanic of the higher Vertebrata. 



Two premaxillaB are always developed. The maxillte are 

 usually present, and may be connected, as in most Batrachia, 

 by quadrato-jugal ossifications with the outer side of the end 

 of the suspensorium, in which an ossification representing 

 the quadi-ate bone is often developed. But the quadrato- 

 jugals (and even the maxillas) 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 Ba- 

 trachia. The suspensorium, which is inclined downwards 

 and forwards in the lower Urodela, passes almost directly 

 downwards, or a little backwards, in the higher, and in the 

 Batrachia slopes greatly backwards ; and it undergoes the 

 same modifications in direction, 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 

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



