146 Mr. H. Seeley on a new Lizard 



overhang and lock on to the zygapophyses of the vertebra in 

 front. Such a structure indicates a flexible vertebral column, 

 for it allows of dorsal vertebrae being supported by the anterior 

 limbs. In the lumbar region of many mammals, such as the 

 Armadillo, the Raccoon, and even the wild Cat, where there is 

 much upward and downward motion, there is a near approach 

 to a like modification of yoking. 



This vertebra, with depressed centrum, obliquely overhanging 

 and transversely oval cup and ball, zygosphene, and zygantrum, 

 indicates the lower dorsal region of a small reptile having its 

 nearest affinities with Iguana. It is f ths of an inch long, not 

 quite so wide in front where widest. It was found in the lower 

 Chalk of Cherry Hiuton, near Cambridge. 



There is no neural spine, and no hypapophysis. 



The inferior surface of the centrum is subtriangular. The 

 length from the base of the cup in front to the base of the ball 

 behind is equal to the width of the zygapophyses in front. 

 From these, two strong curved ridges descend and approximate 

 to the bottom of the sides of the ball. The subtriangular area 

 so enclosed is a little convex transversely and concave in length. 



The vertebra is -roths of an inch high in front, nearly one- 

 half being the height of the centrum, and the remainder that of 

 the neural arch, which is higher behind than in front, and may 

 there have had a slight neural spine. The neural arch on each 

 side is a smooth cupped surface, with a concave border, and 

 contracts behind. 



The anterior zygapophyses are horizontal square surfaces, 

 hardly above the border of the cup, from which they are sepa- 

 rated in front by a perpendicular concavo-convex surface on 

 each side, about the size of their own articulations. 



The zygosphene projects in front of the vertebra, and is just 

 as wide as the cup. Its superior front margin is concave and 

 horizontal. Its flat articular surfaces, which look forward and 

 outward, are very narrow, and entirely between the zygapo- 

 physes, above and in front of which they project about half their 

 own length. 



The neural arch is very thin in front, thicker behind, where 

 the processes are less perfectly preserved. 



The sides of the vertebra are narrow, concave, wedge-shaped 

 surfaces bordered by (1) the basal ridges already mentioned, 

 and (2) the concave ridges at the sides, which from above make 

 the outline of the neural arch, are laterally parallel with its top 

 ridge, and connect the anterior with the posterior zygapophyses. 

 Both ridges meet in front, below the zygapophyses in the 

 tubercle for the rib, which is broken off" on both sides. 



The body of the centrum and the neurapophyses appear to be 



