These plants of the coal period were remarkable, generalized types, connecting classes now widely separated. During this period the insects increase in variety and numbers along with the advancing vegetation. It is interesting to find that as the highest flowering plants are not yet in existence, so those highest orders of insects, the flower-loving and honey-loving ones, such as bees, butterflies and moths, are not yet in existence. Corals and Echinoderms, Molluscs and Crustaceans, etc., continue through the ages with ever shifting forms. Brachiopods have greatly diminished. Foraminifera for the first time assume considerable importance in the earth’s economy. The Molluscan Goniatites continue through this age with changing forms and advancing organization, and are very numerous. The Trilobites, which are characteristic of Palæozoic times, continue under new forms through this age, and then perish. In this age are introduced for the first time typical Crustaceans of the long-tailed kind, such as shrimps. Devonian fishes still prevail. The Elasmobranchii are numerous and varied, and some of them are highly specialized. _Pleuracanthus_ is a remarkable shark which has many features in common with the lung-fishes (Dipnoi), such as the character of the pectoral fins, the shape of the tail, the bones which form a roof for the skull, while the skin is naked. The Dipnoi continue, though in diminished numbers. The Crossopterygians are much less abundant. The Ganoidei increase in numbers and varieties. The fact of greatest interest concerning the Carboniferous period is the _expansion of the true land-breathing, backboned animals, such as the_ =Amphibians=. _Their expansion marks a distinct step forward in the scale of life._ The Carboniferous Amphibia all belong to the extinct order of _Labyrinthodonts_ (_Stegocephala_), in which the skull is well covered with a roof of sculptured bones. The Amphibia of the lower Carboniferous rocks are of small or moderate size, not exceeding eight feet in length and mostly much smaller. A great number of these Amphibians are known, most of them like the Salamanders in shape, but some are snake-like in form, being long and slender. An example of the Stegocephala is _Archegosaurus_.