SKELETON. 



indicates, the dorsal surface is covered, leaving only gaps for the eyes and nostrils. 

 In general the account of the skull given on page 67 ff will apply to these forms, and 

 so far as the dorsal surface is concerned little more needs to be said, aside from the 

 fact that the supratemporal is sometimes transversely divided, that an interparietal 

 foramen occurs (indicating the existence of a parietal eye), that the bones called 

 supraoccipital may be interparietal, and that the sclerotics are common. The 

 floor of the cranium is formed by a large parasphenoid, bordered in front by a pair 

 of (usually toothed) palatines, in front of which are the vomers. Of the carti- 

 laginous parts almost nothing is known; a few, clearly larval forms have well 

 developed branchial arches preserved. 



FIG. 83. Skull of a stegocephalan (Capltosaurus) after Zittell. Letters as in fig. 68. 



Of the GYMNOPHIONES (caecilians) the cartilage skull is known only in Ichthy- 

 ophis; its peculiarities are the reduced parachordals, an ethmoidal nasal septum, 

 a stapes, perforated as in mammals, and alisphenoid and trabecular cartilages more 

 distinct than in most amphibia. Most noticeable of the cartilage bones is the eth- 

 moid, while otics and exoccipitals are fused as are quadrate and pterygoid. The 

 membrane bones form a complete roof to the skull, recalling the stegocephals, but 

 the number of bones is smaller, squamosal, supratemporal, jugal and quadrato- 

 jugal being absent, while a large prefrontal and a larger postfrontal (usually called 

 squamosal) occur. In the roof of the mouth maxillary and palatine are fused, the 

 vomers distinct, while the united parasphenoid and basioccipital form a large os 

 basale. In the lower jaw there are only dentary and angulare, the latter being 

 produced behind the articulare in a remarkable way. 



In the cartilage skull of the URODELES (fig. 82) the pterygoid does not usually 

 reach the anterior part of the skull but projects as a process from the quadrate, 

 which bears, besides the two processes already mentioned (p. 82), a palatobasal 



