broken and undigested scales and bones of small fishes. From their contents, their peculiar external form and markings, and their phosphatic composition, these bodies (coprolites) are recognised as the excrement of some of the larger fishes, and the teeth and scales within them serve to show what were the smaller forms on which these fishes fed (see Fig. 65).

During the Carboniferous period, and indeed throughout the later parts of the Palæozoic ages, the most highly organised creatures living on the globe, so far as we at present know, belonged to the Amphibia-the great class which includes our modern frogs, toads, and salamanders. They belonged, however, to an order that has long been entirely extinct-the Labyrinthodonts, so named from the labyrinthine folds of the internal substance of their teeth. They were somewhat like the existing salamander in form, with weak limbs and a long tail. Their skulls were encased in strong plates of bone, and they likewise carried protective bony scutes on the under sides of their bodies. Those found in Carboniferous rocks are mostly small in size, but some of them, measuring perhaps 7 or 8 feet in length, must have been the monsters of the lagoons, in which they lived. Some of the leading genera are Archegosaurus, Anthracosaurus, Loxomma, Dendrerpeton, Baphetes.

FIG. 146.-Carboniferous Foraminifer (Fusulina cylindrica, f).

The marine life of the Carboniferous period has been extensively preserved in the Carboniferous Limestone, which, as already stated, consists of little else than aggregated remains of organisms. In walking over the surface of the beds of this limestone, one treads upon the floor of the sea in Carboniferous times, with its corals, crinoids, and shells crowded and crushed upon each other. Beginning with the most lowly of these organisms, we may observe abundant remains of foraminifera, which in some portions of the limestone constitute the greater part of the rock. One of their most characteristic forms, named Fusulina (Fig. 146), enters largely into the structure of the limestone across the Old World from Russia to China and Japan, and likewise in North America. Another, called Sacammina, abounds as aggregates of little globular bodies in some parts of the limestone of Britain. Corals have been preserved in prodigious numbers; indeed, some parts of the limestone are almost entirely made up of them. Most of them are rugose kinds, characteristic genera being Zaphrentis, Lithostrotion, (Fig. 147), Clisiophyllum, Lonsdaleia. With these there occur also tabulate forms, including Chatetes, Alveolites, Favosites, etc. Of the sea-urchins, the plates and spines of the genus Archæocidaris (Fig. 148) are specially frequent. But the most common echinoderms are members of the great order of crinoids, which must have grown in thick groves over many square miles of the seabottom. So prodigiously numerous were they that their remains have been aggregated into beds of limestone hundreds of feet in thickness, hence known as crinoidal or encrinite limestone (Fig. 76). The general plant-like form of these animals is shown in Fig.

nus.

b

149. But usually the calcareous joints and plates fell asunder. Frequent genera are named Platycrinus, Poteriocrinus, CyathocriThe Carboniferous seas were tenanted by a peculiar extinct order of echinoderms known as Blastoids or Pentremites (Fig. 150), distinguished from true crinoids by the want of free arms, and by the arrangement of the plates forming the cup. These creatures are characteristically Carboniferous, though they are found also in the higher part of the Silurian system and in Devonian rocks.

The Crustacea of the Carboniferous period presented a strong contrast to those of earlier geological time. In particular, the great family of the Trilobites, so characteristic of the older Palæozoic systems, now died out altogether. Instead of its numerous types in the Silurian and Devonian rocks, it is represented in the Carboniferous system by only four genera, all the species of which are small (Phillipsia, Fig. 151, Griffithides,

Brachymetopus), and none of which rises into the next succeeding system. The most abundant crustaceans were ostracods-an order still abundantly represented at the present day. They are

a

b

FIG. 150. Carboniferous Blastoid (Cup of Pentremite, magnified). (a) View from above; (6) Side view.

FIG. 151. Carboniferous Trilobite (Phillipsia derbiensis, natural size).

minute forms enclosed within a bivalve shell or carapace which entirely invests the body. Many of these live in fresh water; the Cypris, for example, being abundant in ponds and ditches. Others are marine, while some are brackish-water forms. In the Carboniferous lagoons, as at the present time, they lived in enormous numbers; their little seed-like valves are crowded together in some parts of the shale which represents the mud of these lagoons; sometimes they even form beds of limestone. Doubtless, they served as food to the smaller fishes whose remains are usually to be found where the ostracod valves are plentiful. One of the principal genera is Leperditia. There were likewise long-tailed shrimp-like crustaceans (Anthrapalæmon, Palæocrangon), and king-crabs (Prestwichia); while in the earlier part of the period Eurypterids still survived in the waters.

Some of the most delicately beautiful fossils of the Carboniferous limestone belong to the Polyzoa. These animals, of which familiar living examples are the common sea-mats of our shores, are characterised by their compound calcareous or horny framework studded with minute cells, each of which is occupied by a separate individual, though the whole forms one united colony. One of the most abundant Carboniferous genera is Fenestella (Fig. 152). So numerous are the polyzoa in some

bands of limestone as to constitute the FIG. 152. Carboniferous Polyzoon main part of the stone. Their delicate (Fenestella Morrisii, natural size). lace-like fronds are best seen where

the rock has been exposed for a time to the action of the weather; they then stand out in relief and often retain perfectly their rows of cells.

The Brachiopods, so preponderant among the molluscs of the earlier division of Palæozoic time, now decidedly wane before the great advance of the more highly organised lamellibranchs and gasteropods. Some of the most characteristic genera (Fig. 153) are Productus, Spirifera, Streptorhynchus, Rhynchonella, Athyris, Chonetes, Terebratula, Lingula, Discina. Some of the species appear to range over the whole world, for they have been met with across Europe, in China, Australia, and North America. Among these cosmopolitan forms are Productus semireticulatus, Productus longispinus, Streptorhynchus crenistria, Spirifera glabra, Terebratula hastata (Fig. 153).

Some of the more common Lamellibranch molluscs (Fig. 154) belong to the genera Aviculopecten, Leda, Nucula, Edmondia, Modiola, Anthracomya. Among the Gasteropods Euomphalus, Pleurotomaria, Loxonema, and Bellerophon (Fig. 155) are not

FIG. 153. Carboniferous Brachiopods. (a) Productus semireticulatus ();
(b) Streptorhynchus crenistria (3); (c) Spirifera striata ().

infrequent. A pteropod (Conularia, Fig. 156) may be gathered in great numbers in some parts of the Carboniferous Limestone.

FIG. 154.--Carboniferous Lamellibranchs. (a) Edmondia sulcata (); (b) Anthracomya Adamsii (3); (c) Aviculopecten fallax (3).

The Cephalopods were represented by numerous species of Orthoceras, Nautilus, and Goniatites (Fig. 157).