THE SKELETON IN AMPHIBIA. THE SKULL. 175 



the cranium instead of being directed forwards, (2) the 

 maxillae are well developed, and the premaxillae are com- 

 pletely ankylosed together, (3) there are no palatines. 



The skulls of Megalobatrachiis, Cryptobranchus and Siredon 

 resemble those of the highest Urodeles the Salamanders in their 

 wide form, in having the pro-otics distinct from the exoccipitals 

 which are ossified continuously with the epi-otics and opisth- 

 otics, and in having no palatines, but differ in having the two 

 premaxillae separate, and in the arrangement of the vomerine 

 teeth which in Megalobatrachus and Cryptobranchus are placed 

 along the anterior boundaries of the bones, these meeting in 

 the middle line. In Siredon the vomers are separated by the 

 very large parasphenoid. 



The suspensorium in Megalobatrachus and Cryptobranchus 

 projects at right angles to the cranium ; in Siredon it projects 

 somewhat downwards and forwards as in the Salamandrina. 



Modifications of the vomers, pterygoids and palatines ac- 

 company the changes of the larval ichthyoid Siredon into the 

 adult salamandroid Amblystoma, the vomers especially come 

 to resemble to a much greater extent those of the Sala- 

 mandrina. 



The ossification of the skull in the Salamandrina is carried 

 further than in the Ichthyoidea, 4 though the supra-occipital and 

 basi-occipital are not ossified. The skull differs from that in 

 the Ichthyoidea in the size of the part of the vomero-palatines 

 which lies in front of the teeth, in the frequent union of the 

 two premaxillae and in the ossification of all the periotic bones 

 continuously with the exoccipital. 



The skull differs from that of Anura in the following 

 respects : 



(1) the bones of the upper jaw do not form a complete 

 arch standing away from the cranium, and the maxillae are 

 not united to the quadrates by quadratojugals, (2) the long 

 axis of the suspensorium passes obliquely downwards and 

 forwards instead of downwards and backwards, (3) there is no 



