THE SKELETON IN AMPHIBIA. THE SKULL. 177 



the temporal and other fossae has taken place. In many 

 forms the surface of the bones is as in Crocodiles, strongly 

 sculptured (fig. 27, right half) with ridges and grooves which 

 probably lodged sensory organs. The bones forming the 

 roof of the skull are generally very uniform in size, perhaps 

 the most noticeable of them being the paired dermo-supra- 

 occipitals (fig. 27, 19). Paired dermo-supra-occipitals occur 

 also in certain Ganoids. The Labyrinthodont skull also 

 bears resemblance to that of many fish in the development 

 of a pair of long pointed epi-otics (fig. 27, 18), which remain 

 permanently distinct from the surrounding bones. The pa- 

 rietals are small and enclose between them the interparietal 

 foramen (fig. 27, 13). In some forms in which the head is 

 protected with an armour of scutes, these do not roof over 

 the interparietal foramen, and from this fact it has been 

 inferred that the Labyrinthodonts had a functional pineal 

 eye. Both supra- and infra-temporal fossae are partially or 

 completely roofed over by the postorbitals and large supra- 

 temporals (fig. 27, 15). 



There is generally a ring of bones in the sclerotic coat 

 of the eye. The pterygoids do not meet in the middle line, 

 being separated by the parasphenoid. The palatines bear 

 teeth, and in some genera (Arckegosaurus) form long splints 

 lying along the inner side of the maxillae and more or less 

 surrounding the posterior nares. In others (Nyrania) they 

 lie in the normal position near the middle line, one on 

 each side of the parasphenoid. The vomers bear teeth and 

 sometimes meet in the middle line ; they are sometimes 

 confluent with the parasphenoid. On the ventral surface 

 of the cranium there are generally large palatal vacui- 

 ties. 



In the mandible there is often a well-marked postglenoid 

 process, and the articular is generally completely ossified. 



GrYMNOPHioNA. The skull bears a considerable resemblance 

 to that of Labyrinthodonts, especially in the arrangement of 

 R. 12 



