[Illustration: Fig. 51.--Odontopteris Brardii.] [Illustration: Fig. 52.--Sphenopteris artemisiæfolia, magnified.] Among the corals of the period, we may include the genera _Lithostrotion_ and _Lonsdalea_, of which _Lithostrotion basaltiforme_ (Fig. 58), and _Lonsdalea floriformis_ (Fig. 59), are respectively the representatives, with _Amplexus coralloïdes_. Among the Polyzoa are the genera _Fenestrella_ and _Polypora_. Lastly, to these we may add a group of animals which will play a very important part and become abundantly represented in the beds of later geological periods, but which already abounded in the seas of the Carboniferous period. We speak of the _Foraminifera_ (Fig. 60), microscopic animals, which clustered either in one body, or divided into segments, and covered with a calcareous, many-chambered shell, as in Fig. 60, _Fusulina cylindrica_. These little creatures, which, during the Jurassic and Cretaceous periods, formed enormous banks and entire masses of rock, began to make their appearance in the period which now engages our attention. [Illustration: Fig. 53.--Producta Martini. One-third nat. size.] [Illustration: Fig. 54.--Bellerophon costatus. Half nat. size.] [Illustration: Fig. 55.--Goniatites evolutus. Nat. size.] [Illustration: Fig. 56.--Bellerophon hiulcus.] [Illustration: Fig. 57.--Orthoceras laterale.] [Illustration: Fig. 58.--Lithostrotion basaltiforme.] [Illustration: Fig. 59.--Lonsdalea floriformis.] The plate opposite (PLATE X.) is a representation of an ideal aquarium, in which some of the more prominent species, which inhabited the seas during the period of the Carboniferous Limestone, are represented. On the right is a tribe of corals, with reflections of dazzling white: the species represented are, nearest the edge, the _Lasmocyathus_, the _Chætetes_, and the _Ptylopora_. The Mollusc which occupies the extremity of the elongated and conical tube in the shape of a sabre is an _Aploceras_. It seems to prepare the way for the Ammonite; for if this elongated shell were coiled round itself it would resemble the Ammonite and Nautilus. In the centre of the foreground we have _Bellerophon hiulcus_ (Fig. 56), the _Nautilus Koninckii_, and a _Producta_, with the numerous spines which surround the shell. (See Fig. 62.) [Illustration: Fig. 60.--Foraminifera of the Mountain Limestone, forming the centre of an oolitic grain. Power 120.] [Illustration: Fig. 61.--Foraminifera of the Chalk, obtained by brushing it in water. Power 120.] On the left are other corals: the _Cyathophyllum_ with straight cylindrical stems; some Encrinites (_Cyathocrinus_ and _Platycrinus_) wound round the trunk of a tree, or with their flexible stem floating in the water. Some Fishes, _Amblypterus_, move about amongst these creatures, the greater number of which are immovably attached, like plants, to the rock on which they grow. [Illustration: X.--Ideal view of marine life in the Carboniferous Period.]