Taking the Miocene flora as a whole, Dr Heer concludes from his study of about 3000 plants contained in the European Miocene alone, that the Miocene plants indicate tropical or sub-tropical conditions, but that there is a striking inter-mixture of forms which are at present found in countries widely removed from one another. It is impossible to state with certainty how many of the Miocene plants belong to existing species, but it appears that the larger number are extinct. According to Heer, the American types of plants are most largely represented in the Miocene flora, next those of Europe and Asia, next those of Africa, and lastly those of Australia. Upon the whole, however, the Miocene flora of Europe is mostly nearly allied to the plants which we now find inhabiting the warmer parts of the United States; and this has led to the suggestion that in Miocene times the Atlantic Ocean was dry land, and that a migration of American plants to Europe was thus permitted. This view is borne out by the fact that the Miocene plants of Europe are most nearly allied to the living plants of the eastern or Atlantic seaboard of the United States, and also by the occurrence of a rich Miocene flora in Greenland. As regards Greenland, Dr Heer has determined that the Miocene plants indicate a temperate climate in that country, with a mean annual temperature at least 30° warmer than it is at present. The present limit of trees is the isothermal which gives the mean temperature of 500 Fahr. in July, or about the parallel of 67° N. latitude. In Miocene times, however, the Limes, Cypresses, and Plane-trees reach the 79th degree of latitude, and the Pines and Poplars must have ranged even further north than this. The _Invertebrate Animals_ of the Miocene period are very numerous, but they belong for the most part to existing types, and they can only receive scanty consideration here. The little shells of _Foraminifera_ are extremely abundant in some beds, the genera being in many cases such as now flourish abundantly in our seas. The principal forms belong to the genera _Textularia_ (fig. 237), _Robulina, Glandulina, Polystomella, Amplistegina_, &c. Corals are very abundant, in many instances forming regular "reefs;" but all the more important groups are in existence at the present day. The Red Coral (_Corallium_), so largely sought after as an ornamental material, appears for the first time in deposits of this age. Amongst the _Echinoderms_, we meet with Heart-Urchins (_Spatangus_), Cake-Urchins (_Scutella_; fig. 238), and various other forms, the majority of which are closely allied to forms now in existence. [Illustration: Fig. 237.--_Textularia Meyeriana_, greatly enlarged. Miocene Tertiary.]