268 



CLASS AMPHIBIA. 



they are processes. The hyoid is attached dorsally, directly or 

 by ligament, to the auditory capsule or to the quadrate. 



In the Urodela the cartilaginous cranium is much reduced. Cartilage 

 is found in the roof and floor of the skull in the occipital region only. In 

 front the trabeculae remain separate both dorsally and ventrally, so that 

 there are large supracranial and basicranial fontanelles filled in by the 

 overlying membrane bones (parietals, frontals, and parasphenoid). In 

 some of the lower forms (Proteus, Necturus) the trabeculae retain through- 

 out life the form of narrow cartilaginous bars. The auditory capsules 

 possess a prootic and one or more other periotic bones, and in the anterior 



FIG. 145. A dorsal, B ventral, C side view of the skull of the newt (Triton cristatus) x 2 

 (after Parker, from Reynolds). The cartilage is dotted, the cartilage bones are marked 

 with dots and dashes, the membrane bones are white. 1 premaxilla ; 2 anterior nares ; 

 3 internal nares ; 4 nasal ; 5 frontal ; 6 parietal ; 7 prelronto-lacrymal ; 8 maxilla ; 

 #vomero-palatine ; 10 parasphenoid ; 11 orbitosphenoid ; 12 pterygoid ; 13 squamosal ; 

 14 prootic region of exoccipito-periotic bone ; 15 quadrate ; 16 quadrate cartilage ; 17 

 exoccipital region of exoccipito-periotic ; 18 articular ; 19 articular cartilage ; 20 dentary ; 

 21 splenial ; 22 middle narial passage ; II, V, VII, IX, X. foramina for'exitloi corresponding 

 cranial;, nerves. 



part of the sphenoid region there is a cartilage bone, the'orbitosphencid 

 (Fig. 145, 11) The ethmoid region (nasal capsules) is unossified. The 

 parietals and frontals are separate bones and the parasphenoid is not 

 dagger -shaped. The vomer is double and usually fused with the palatine 

 (Fig. 145, 9). There is a prefrontal in front of the orbit, with which a 

 lacrymal element is supposed to be fused (7). There is a palato-pterygoid 

 bar in the larva, but in the adult the pterygoid and palatine bones are 

 usually not connected. The quadrato-jugal is represented by ligament 

 only. In the lower forms the quadrate is directed forwards as in the larva 

 of all Amphibia, but in the higher forms it stands out at right angles or 



