204. Forms of Cretaceous _Ammonitidoe_.
205. _Belemnitella mucronata_.
206. Tooth of _Hybodus_.
207. Fin-spine of _Hybodus_.
208. _Beryx Lewesiensis_ and _Osmeroides Mantelli_.
209. Teeth of _Iguanodon_.
210. Skull of _Mosasaurus Camperi_.
211. _Chelone Benstedi_.
212. Jaws and vertebrae of _Odontornithes_.
213. Fruit of _Nipadites_.
214. _Nummulina loevigata_.
215. _Turbinolia sulcata_.
216. _Cardita planicosta_.
217. _Typhis tubifer_.
218. _Cyproea elegans_.
219. _Cerithium hexagonum_.
220. _Limnoea pyramidalis_.
221. _Physa columnaris_.
222. _Cyclostoma Arnoudii_.
223. _Rhombus minimus_.
224. _Otodus obliquus_.
225. _Myliobatis Edwardsii_.
226. Upper jaw of Alligator.
227. Skull of _Odontopteryx toliapicus_.
228. _Zeuglodon cetoides_.
229. _Paloeotherium magnum_, restored.
230. Feet of _Equidoe_.
231. _Anoplothelium commune_.
232. Skull of _Dinoceras mirabilis_.
233. _Vespertilio Parisiensis_.
234. Miocene Palms.
235. _Platanus aceroides_.
236. _Cinnamomum polymorphum_.
237. _Textularia Meyeriana_.
238. _Scutella subrotunda_.
239. _Hyalea Orbignyana_.
240. Tooth of _Oxyrhina_.
241. Tooth of _Carcharodon_.
242. _Andrias Scheuchzeri_.
243. Skull of _Brontotherium ingens_.
244, _Hippopotamus Sivalensis_.
245. Skull of _Sivatherium_.
246. Skull of _Deinotherium_.
247. Tooth of _Elephas planfrons_ and of _Mastodon
Sivalensis_.
248. Jaw of _Pliopithecus_.
249. _Rhinoceros Etruscus_ and _R. megarhinus_.
250. Molar tooth of _Mastodon Arvernensis_.
251. Molar tooth of _Etephas meridionalis_.
252. Molar tooth of _Elephas antiquus_.
253. Skull and tooth of _Machairodus cultridens_.
254. _Pecten Islandicus_.
255. Diagram of high-level and low-level gravels.
256. Diagrammatic section of Cave.
257. _Dinornis elephantopus_.
258. Skull of _Diprotodon_.
259. Skull of _Thylacoleo_.
260. Skeleton of _Megatherium_.
261. Skeleton of _Mylodon_.
262. _Glyptodon clavipes_.
263. Skull of _Rhinoceros tichorhinus_.
264. Skeleton of _Cervus megaceros_.
265. Skull of _Bos primigenius_.
266. Skeleton of Mammoth.
267. Molar tooth of Mammoth.
268. Skull of _Ursus speloeus_.
269. Skull of _Hyoena speloea_.
270. Lower jaw of _Trogontherium Cuvieri_.

PART I.

PRINCIPLES OF PALAEONTOLOGY.

INTRODUCTION.

THE LAWS OF GEOLOGICAL ACTION.

Under the general title of "Geology" are usually included at
least two distinct branches of inquiry, allied to one another in
the closest manner, and yet so disti