SKELETON. 8 3 
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. 
Fic. 83.—Skull of a stegocephalan (Capitosaurus) after Zittell. Letters as in fig. 68. 
Of the GyMNopPHIONES (cecilians) 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 
