The Rhytina was probably intermediate between the Dugong and the Manatee, judging from the casts of its brain-cavity. Its brain was very small considering the size of the animals. Altogether, as many as fourteen fossil genera and thirty species are known. Evidently, then, the old Sirenia were once a much more flourishing race. At present, they are confined exclusively to the tropical regions of the earth, and their past distribution, as revealed to the geologists, adds one more proof to the now well-established fact, that throughout most of the Tertiary era the climate of northern latitudes was very much warmer than now—in fact, sub-tropical. What cause, or causes, brought about so great a change, we cannot stay to consider here.
In conclusion, it only remains to express a hope that the reader may have been interested in our humble endeavours to describe some of the largest, most strange, and wonderful forms of life that in remote ages have found a home on this planet. And perhaps a few of our readers may be induced to add a new and never-failing interest to their lives by searching in the stony record for traces of the world’s “lost creations.” If so, our labour will not have been in vain.
Table of Stratified Rocks.
| Periods. | Systems. | Formations. | |||||
| Quaternary. | RECENT |  | Terrestrial, Alluvial, Estuarine, and Marine Beds of Historic, Iron, Bronze, and Neolithic Ages | Dominant type, Man | |||
| PLEISTOCENE |  | Peat, Alluvium, Loess Valley Gravels, Brickearths Cave-deposits Raised Beaches Palæolithic Age Boulder Clay and Gravels | |||||
| CAINOZOIC. Tertiary. | PLIOCENE |  | Norfolk Forest-bed Series Norwich and Red Crags Coralline Crag (Diestian) | Dominant types, Birds and Mammals | |||
| MIOCENE | Œningen Beds Freshwater, etc. | ||||||
| EOCENE | |
| |||||
| SECONDARY, OR MESOZOIC. | CRETACEOUS | | Maestricht Beds Chalk Upper Greensand Gault | ||||
| |||||||
| JURASSIC | | Purbeck Beds Portland Beds Kimmeridge Clay (Solenhofen Beds) Corallian Beds Oxford Clay Great Oolite Series Inferior Oolite Series Lias | Dominant type Reptilia | ||||
| TRIASSIC | | Rhætic Beds Keuper Muschelkalk Bunter | |||||
| PRIMARY, OR PALÆOZOIC. | PERMIAN or DYAS | |
| Dominant type,Fishes | |||
| Red Sandstone and Conglomerate Rothliegende | |||||||
| CARBONIFEROUS | | Coal Measures and Millstone Grit Carboniferous Limestone Series | |||||
| DEVONIAN & OLD RED SANDSTONE | | Upper Old Red Sandstone Devonian Lower Old Red Sandstone | |||||
| SILURIAN | | Ludlow Series Wenlock Series Llandovery Series May Hill Series | |||||
| ORDOVICIAN | | Bala and Caradoc Series Llandeilo Series Llanvirn Series Arenig and Skiddaw Series | |||||
| CAMBRIAN | | Tremadoc Slates Lingula Flags Menevian Series Harlech and Longmynd Series | |||||
| EOZOIC-ARCHÆAN | | Pebidian, Arvonian, and Dimetian Huronian and Laurentian | Dominant type, Invertebrata | ||||
THE GREAT SEA-SERPENT.