THE AMPHIBIAN SKULL. 



163 



other Vertebrata. Turbinal ossifications are developed in the 

 cartilage bounding the nasal capsules in some Amphibia. 



Viiix 



Prmr 



Fie. S5. — Skull of Itwnu esauienta. A^ from above; B, from below ; G. from tbe left Bide 

 03, pai-asphenold ; y, gtrdle-bone; Z, *be " temporo-mastoid.'' 



The membrane bones of the Amphibian skull are : 1. Front- 

 als and parietals, which, in the £atrachia, may be fused to- 

 gether into one bone. 2. Nasals are generally present. 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 skuU from the 

 occipital to the ethmoidal region, as in Teleostei and Ganoidei. 



5. A membrane bone {Z), called " temporo-mastoid " by Du- 

 g^s, lies on the outer side of the suspensorium, 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 preopercu- 

 lum of fishes, and to the tjrmpanic of the higher Vertebrata. 



Two premaxillse are always developed. The maxillae are 

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

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

 of the suspensorium, in whi6h an ossification representing tho 



