296 FOSSIL REPTILES. 



odontoid process ; their anterior face has a concavity propor- 

 tioned to the convexity of the preceding vertebrae, with some 

 other small variations. 



The dorsal, after the second, have always a square dorsal 

 crest, an anterior face concave, and a posterior convex, both 

 kidney- formed, and horizontal articular apophyses, the lower 

 facing downwards, the anterior one upwards. On each side, 

 under the anterior, the whole transverse apophysis consists in a 

 tubercle oval-formed, and vertically directed to support the rib. 



Of these vertebrae there are twenty-two, and no lumbar, 

 though there are twenty-seven pairs of ribs, including the five 

 cervical, but the first and last are very small. The total ab- 

 sence of lumbar vertebrae seems to be a general rule in this 

 family. There are but two sacral vertebrae in the monitor. 

 The caudal vertebrae after the eighth are very numerous, being 

 sixty-six, eighty, and upwards. They are easily recognized by 

 their spinous and transverse apophyses being long and narrow, 

 and their articulary apophyses almost vertical. 



The differences which characterize the vertebrae of the various 

 subgenera consist chiefly in the respective length and bulk of 

 their bodies, and the respective length and breadth of their 

 apophyses. 



The ribs of lizards are slender and round, and the anterior 

 ones alone have the costal head a little bulky and compressed. 



A remark worthy of being made here is, that a great number 

 of the caudal vertebrae of the lizards proper are divided verti- 

 cally, in the middle, into two portions, which are separated very 

 easily, even more easily than any two distinct vertebrae at the 

 place of their articulation, because this articulation is compli- 

 cated, formed by many apophyses, and strengthened by liga- 

 ments, while in the other case a separation is prevented only 

 by the periosteum and the surrounding tendons. This is, pro- 

 bably, the cause that the tails of lizards are so easily broken. 

 The tail will grow again after it has been broken, but neither 

 its skeleton nor teguments continue of the same quality. The 



