244 UPPER, OR FLINTY CHALK. 



but not the slightest trace of another process could be discovered. This 

 circumstance puzzled me exceedingly ; and the difficulty of explaining it 

 was increased, upon perceiving that the apophyses in question were per- 

 fectly anchylosed to the bodies of the vertebrae, and not united by suture, 

 as in the recent lacertee. A careful perusal of Cuvier's observations on 

 the osteological characters of the monitor of Maestricht, enabled me, how- 

 ever, to explain this apparent want of agreement, in a very satisfactory 

 manner ; the researches of that philosopher having shewn that the posterior 

 caudal vertebrcB possess the structure here described, " Vos en chevro7i n'y 

 est plus articulS, mais soudS, et fait corps avec elks." The situation of this 

 inferior process, presents also another striking proof of the identity of the 

 vertebrae before us, with those of the INIaestricht monitor. In the lizard 

 tribe in general, the chevron bone is placed at the junction of the vertebrae ; 

 and in the monitor, at the posterior part ; but in the animal of St. Peter's 

 mountain, it is attached to the middle of the vertebrae, as in the specimens 

 before us. 



That the reader may form his own opinion upon this interesting 

 subject, Cuvier's anatomical description of the vertebral column of the 

 Maestricht animal, is here subjoined. The extract is rather long, but it 

 will not be deemed irrelevant, when the importance of extreme accuracy 

 in these researches is duly considered. 



" Toutes ces vertebres, comme celles des crocodiles, des monitors, des 

 inguanes, et en general de la plupart des sauriens, et des ophidiens, ont 

 leur corps concave en avant, et convexe en arriere, ce qui les distingue 

 deja notablement de celles des cetaces qui I'ont a-peu-pr^s jo/awe, et bien 

 plus encore de celles des poissons, oii il est creus6 des deux c6tes en cone 

 concave. 



" Les anterieures ont cette convexit6 et cette concavit6 beaucoup plus 

 prononcees que les posterieures. Quant aux apophyses, leur nombre 

 etablit cinq sortes de ces vertebres. 



"Les premieres, ont une apophyse epineuse superieure, longue et 

 comprimee ; une inferieure terminee par une concavite ; quatre articulaires 

 dont les posterieures sont plus courtes et regardent de dehors, et deux 



