Fig. 95.
Fig. 95. Comptonia acutiloba, apparently the leaf of a plant belonging to the natural order Proteaceæ, which abound in Australia, and are also found at the Cape of Good Hope at the present day.
Figures 96 to 99 show the leaves of plants belonging to the Miocene epoch.
Fig. 96. Fig. 97.
Fig. 98.
Fig. 96. Acer trilobatum, a three-lobed palmate leaf, like that of the Maple, with the lobes unequal, inciso-dentate, the lateral ones spreading, found at Œningen. Fig. 97. Ulmus Bronnii, a petiolate leaf, like that of the Elm, unequally ovato-acuminate, feather-veined and toothed, found in Bohemia. Fig. 98. Rhamnus Aizoon, a petiolate elliptical obtuse feather-veined leaf, with an entire margin, found in Styria.
The most striking characters of the Miocene epoch consist in the mixture of exotic forms of warm regions with those of temperate climates. Unger says that it resembles that of the southern part of North America. Thus we meet with Palms, such as species of Flabellaria and Phœnicites, a kind of Bamboo called Bambusium sepultum; Lauraceæ, as Daphnogene and Laurus; Combretaceæ, as Getonia and Terminalia; Leguminosæ, as Phaseolites, Desmodophyllum, Dolichites, Erythrina, Bauhinia, Mimosites, and Acacia—all plants having their living representatives in warm climates; Echitonium, Plumiera, and other Apocynaceæ of equatorial regions; Comptonia (Fig. 95), a Proteaceous genus, and Steinhauera, a Cinchonaceous genus; mingled with species of Acer (Fig. 96), Ulmus (Fig. 97), Rhamnus (Fig. 98); and Amentiferous forms, such as Myrica, Betula, Alnus (Fig. 99), Quercus, Fagus, Carpinus, all belonging to temperate and cold climates. The statements as to the occurrence of Pinus sylvestris and Betula alba among the Miocene fossils have not been founded on complete data. It is by no means easy, even in the present day, to distinguish fragments of dried specimens of Pinus Pumilio from those of P. sylvestris, and from a great many other Pines. The difficulty is still greater in fossils (Hook. Kew Journ. v. 413). There are a very small number of plants belonging to orders with gamopetalous corollas. In the Miocene formation of Lough Neagh in Ireland, and of Mull in Scotland, silicified trunks of considerable size have been found. The Irish silicified wood has been denominated Cupressoxylon Pritchardi from its apparent resemblance to the Cypress. As connected with the Miocene epoch, we may notice the leaf-beds found at Ardtun, in the island of Mull, by the Duke of Argyll.[22] Above and below these beds basalt occurs, and there are peculiar tuff-beds alternating with the leafy deposits. These tuff-beds were formed by the deposit of volcanic dust in pools probably of fresh water. They contain fragments of chalk and flint. The leaves are those of plants allied to the Yew, Rhamnus, Plane, and Alder, along with the fronds of a peculiar Fern, and the stems of an Equisetum. The genera are Taxites or Taxodites (Fig. 100), Rhamnites (Fig. 101), Platanites, Alnites, Filicites, and Equisetum (Fig. 102). In the leaf-beds at Bournemouth Mr. Wanklyn detected several ferns. One is a species of Didymosorus, and shows distinct venation and fructification. Fossilised wood was found in the Arctic Regions by Captain M'Clure. At the N.W. of Banks Land he found trees with trunks 1 foot 7 inches in diameter.
