446 Notices respecting Ne-jo Books. 



The author then describes in detail the organization of the teeth of 

 this animal, after which he proceeds. 



If we attempt to discover among the recent lizards a dentature at 

 all analogous, we shall find among the Iguanas alone any kind of 

 resemblance ; yet even here we cannot fail to remark, that in this as 

 in every other instance, if there be a general analogy, there are also 

 striking and important differences in the structure of the jirimitive 

 animals of our planet, and of those which are its present inhabitants. 

 Of the Iguana there are several species ; but the only skull we have 

 had an opportunity of examining, is that of an individual from Bar- 

 badoes, we believe of I. tuberculata * . Fig. 6. Plate XX. is a view of 

 the inner surface of the right side of the upper jaw of this animal, of 

 the natural size, and which is magnified four diameters at fig. 5 ■\. 

 The teeth are slightly convex externally, and have a ridge down the 

 middle ; they are slightly concave on the inner surface ; difl^'erent 

 views of the crown of a tooth are seen, largely magnified, in fig. 4. 

 Plate XVII. In the angular form of the crown and its serrated edges, 

 they strikingly resemble the fossil, fig. 1 1. of the same plate. The new 

 teeth are formed at the bases of the old ones, and lie in a depression 

 at the root of the fang, as is beautifully shown in the magnified draw- 

 ing, fig. '). The jaw throws up a lateral parapet on the outside of the 

 teeth; but they have no alveoli, nor any internal protection but the 

 gum. From the above observations, it appears that the fossil teeth 

 bear a greater analogy to those of the recent Iguana, both in their 

 form and in the process by which dentition is effected, than to those 

 of the crocodiles, monitors, and other living saurians. But notwith- 

 standing this general resemblance, the remarkable characters resulting 

 from the act of mastication, separate the original animal from all known 

 genera. None of the existing reptiles perform mastication ; their 

 food or prey is taken by the teeth or tongue ; so that a moveable co- 

 vering of the jaws, similar to the lips and cheeks of the mammalia, is 

 not necessary, either for confining substances subjected to the action 

 of teeth as organs of mastication, or for the purposes of seizing or 

 reaching food +. The herbivorous amphibice gnaw off the vegetable 

 productions on which they feed, but do not chew them. Now ' as 

 €very organic individual forms an entire system of its own, all the 



* Oss. Foss. vol. v. Plate XVF. Figs. 24, 25. 



" The Iguanas are natives of many parts of America and the West India 

 Islands, and are rarely met with any where north or south cf the tropics. 

 They are from three to five feet long from the end of the snout to the tip 

 of the tail. They inhabit rocky and woody places, and feed on insects and 

 vegetables. Many of the Bahama islands abound with them; they nestle 

 in hollow rocks and trees; their eggs have a thin skin like those of the 

 turtle. Though they are not amphibious, they are said to keep under water 

 an hour. When they swim they do not use their feet, but place them close 

 to their body, and guide themselves with their tails ; they swallow all they 

 eat whole. They are so impatient of cold, that they scarcely appear out of 

 their holes but when the sun shines." Shaw's Zoology, vol. iii. p. 199. 



-|- We are indebted to the kindness of Mr. C'lift for the original drawings 

 of thess parts of the recent Iguana. 



X Recs's Cyclopffid. art. "Reptiles." 



parts 



