THE MIOCENE PERIOD. 311 



can 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 tem- 

 perature at least 30 warmer than it is at present. 



The present limit of trees is the isothermal which gives the 

 mean temperature of 50 Fahr. in July, or about the parallel 

 of 67 N. latitude. In Miocene times, however, the Eimes, 

 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, Poly- 

 stomella, Amphistegina, &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 (Cor- 

 allium\ so largely sought 

 after as an ornamental ma- 

 terial, appears for the first 

 time in deposits of this age. 

 Amongst the Echinoderms, 

 we meet with Heart -Urchins (Spatatigus), Cake - Urchins 

 (Scutel/a, fig. 238), and various other forms, the majority of 

 which are closely allied to forms now in existence. 



Numerous Crabs and Lobsters represent the Crustacea; but 

 the most important of the Miocene Articulate Animals are the 

 Insects. Of these, more than thirteen hundred species have 

 been determined by Dr Heer from the Miocene strata of 

 Switzerland alone. They include almost all the existing 

 orders of insects, such as numerous and varied forms of 

 Beetles (Coleoptera\ Forest-bugs (Hemiptera}, Ants (flytnen- 

 optera), Flies (Diptera}, Termites and Dragon -flies (Netirop- 

 tera], Grasshoppers (Orthoptera\ and Butterflies (Lepidoptera). 



