The Sirenians are an ancient race, for their remains have been found in Tertiary strata, of various ages, from Eocene to Pleistocene, over the greater part of Europe--in England, Holland, Belgium, France, Germany, Austria, and Italy; also near Cairo. In the New World, fossil Sirenians have been found in South Carolina, New Jersey, and Jamaica.
Another European species is the Halitherium, from the Miocene rocks of Hesse-Darmstadt, of which a cast may be seen in the Natural History Museum, South Kensington. Its length is 7 ft. 8 in. The teeth in this form resembled those of the Dugong.
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.
------------------------------------------------------------------------ Periods. | Systems. | Formations. | ------------+------------------+-------------------------------+-------- Quaternary. | { |Terrestrial, Alluvial, | |=RECENT= { | Estuarine, and Marine Beds of | | { | Historic, Iron, Bronze, and | | { | Neolithic Ages | | | | | { |Peat, Alluvium, Loess |Dominant | { |Valley Gravels, Brickearths | type, | { |Cave-deposits |Man |=PLEISTOCENE= { |Raised Beaches | | { |Palæolithic Age | | { |Boulder Clay and Gravels | ------------+------------------+-------------------------------+-------- CAINOZOIC. | { |Norfolk Forest-bed Series | Tertiary. |=PLIOCENE= { |Norwich and Red Crags | | { |Coralline Crag (Diestian) | | | | |=MIOCENE= |Oeningen Beds Freshwater, etc. | | | | | { |Fluvio-marine Series | | { | (Oligocene) |Dominant |=EOCENE= { |Bagshot Beds }(Nummulitic | types, | { |London Tertiaries } Beds) |Birds ------------+------------------+-------------------------------| and SECONDARY, | { |Maestricht Beds |Mammals OR MESOZOIC.| { |Chalk | |=CRETACEOUS= { |Upper Greensand | | { |Gault | | { |Lower Greensand } Neocomian | | { |Wealden } | |------------------+-------------------------------+-------- | { |Purbeck Beds | | { |Portland Beds | | { |Kimmeridge Clay | | { | (Solenhofen Beds) | |=JURASSIC= { |Corallian Beds | | { |Oxford Clay |Dominant | { |Great Oolite Series | type | { |Inferior Oolite Series |Reptilia | { |Lias | |-------------- ---+-------------------------------| | { |Rhætic Beds | |=TRIASSIC= { |Keuper | | { |Muschelkalk | | { |Bunter | ------------+------------------+-------------------------------+-------- PRIMARY, |=PERMIAN or { |Red Sandstone, Marl } | OR |DYAS= { |Magnesian Limestone, }Zechstein| | { | etc. } |Dominant PALÆOZOIC. | { |Red Sandstone and Conglomerate | type, | { |Rothliegende |Fishes | | | |=CARBONIFEROUS= { |Coal Measures and Millstone | | { | Grit | | { |Carboniferous Limestone Series | | | | |=DEVONIAN & OLD { |Upper Old Red Sandstone | | 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 |Dominant | { | Dimetian | type, | { |Huronian and Laurentian |Inverte- | | | brata ------------+------------------+-------------------------------+--------