574 REPTILIA [CH. 



with one another and thence the division of the mouth cavity into 

 an air-passage above and a food-passage below remains incomplete. 



The end of Meckel's cartilage which articulates with the quad- 

 rate is converted into a bone, the articular. Three pairs of the 

 hinder visceral arches are preserved. These retain their rod-like 

 form as in Urodela, the median connecting pieces (copulae) remain- 

 ing small. 



The membrane bones of the skull are one of its most character- 

 istic features. The roofing bones are the same as in the Urodela 

 paired nasals, frontals and parietals. On the roof of the mouth 

 there are two vomers and a parasphenoid. The vomers, however, 

 are rod-like, toothless and placed close together, and the para- 

 sphenoid is a small rudiment. 



The bones of the side of the head and the upper lip form a most 

 peculiar scaffolding which is widely separated from the cranium. 

 The lizard is in an intermediate condition between the Cotylosauria 

 or most primitive fossil Reptiles, in which as in the Amphibian 

 Stegocephala a continuous sheet of bones extends from the cranium 

 to the upper lip, and modern Amphibia, where all those bones have 

 disappeared, leaving a large vacuity between the cranium and upper 



HP. 



In front in the upper lip there isapremaxilla bearing teeth 

 followed by a maxilla in which there are also teeth. The maxilla 

 is joined to the pterygoid by an ectopterygoid or transverse 

 bone. Between the maxilla and frontal on the side of the face are two 

 b'ones known as prefrontal and lachrymal. The line of bones in 

 the upper lip is continued by the jugal. This unites with a bone 

 placed behind the eye termed the postfrontal, which joins both the 

 frontal and parietal. Thus the eye is surrounded by a ring of bone. 

 In some of the larger Lacertilia though not in Lacerta this ring is 

 completed by a minute postorbital bone which intervenes between 

 the jugal and postfrontal. 



The squamosal is a characteristic V-shaped bone. The apex 

 of the V articulates with the upper side of the quadrate : of the 

 two arms one is directed forwards and meets the postfrontal, thus 

 forming a bony bar parallel to the cranium which is called the upper 

 temporal arcade. The other limb is directed backwards and 

 inwards and meets a crest on the parietal so that a bridge is formed 

 extending over the hinder part of the cranium. The limb seems 

 to have been a distinct bone to which the name tabulare has 

 been given. The space in the dried skull existing between this 



