XXIIl] LACERTA ViVIPARA 575 



bridge and the cranium is called the post-temporal fossa. In 

 many Reptiles, including most Lacertilia, there is a similar space 

 between the cranium and the lateral bridge formed by the junction 

 of the squamosal and postfrontal which is termed the supratem- 

 poral fossa. This space is roofed over in Lacerta by two dermal 

 bones called supratemporals which are not to be confounded 

 with the bones bearing this name in Pisces. They are osteoderms, 

 and the sole remnants of a once continuous covering of these bones. 



Finally, the space intervening between the quadrate and jugal on 

 the side of the. face is known as the laterotemporal fossa. In 

 Spkenodon, Crocodilia and a very large number of extinct Reptiles it 

 is bounded below by a quadratojugal bone which joins the jugal 

 to the quadrate. When the quadratojugal is present the series of 

 bones consisting of maxilla, jugal and quadratojugal is known as the 

 lower temporal arcade. The upper temporal arcade is formed 

 as we have seen by the postfrontal and the squamosal. The loss of 

 the quadratojugal in Lacertilia is doubtless connected with the 

 greater mobility of the jaws. In some Lizards, notably in Geckos, 

 the quadrate can move slightly on its articulation with the skull, 

 as can also the pterygoid on the basipterygoid process. When 

 the lower jaw is pulled downwards and backwards by its depressor 

 muscle it tends to throw the lower end of the quadrate slightly 

 forwards : the pterygoid slides on the basisphenoid, and pushing 

 the ectopte^goid tilts the maxilla slightly upwards. With the 

 maxilla all the other bones of the face move, and the membranous 

 interorbital septum permits the ethmoidal region of the cranium to 

 be slightly bent on the hinder portion. 



The cartilaginous lower jaw is ensheathed by five distinct 

 membrane bones. The dentary and splenial occupy the same 

 positions as in Teleostomi and Urodela. The angular clamps the 

 under side of the articular, which is the cartilage bone replacing 

 the upper end of the cartilaginous jaw. The supra-angular 

 lies above the angular on the outer side of the articular. The 

 coronoid is a small projection on the upper edge of the jaw. 



The pectoral girdle is at first sight exceedingly complicated, but 

 in reality it consists of the same parts as in the Anura. Above the 

 cavity for articulation of the arm the glenoid cavity there is the 

 cartilaginous scapula; below the girdle forks into acoracoid and 

 precoracoid united by an epicoracoid. The cartilage bones present 

 are the scapula, precoracoid and coracoid. The cartilage above 

 the scapular bone is slightly calcified but is not converted into 



