Fig. 127.—Carboniferous Braciopoda. a, Producta semireticulata, showing the slightly concave dorsal valve; a' Side view of the same, showing the convex ventral valve; b, Producta longispina; c, Orthis resupinata; d, Terebratula hastata; e, Athyris subtilita; f, Chonetes Hardrensis; g, Rhynchonella pleurodon; h, Spirifera trigonalis. Most of these forms are widely distributed in the Carboniferous Limestone of Britain, Europe, America, &c. All the figures are of the natural size. (After Davidson, De Koninck, and Meek.) the spines were actually employed as organs of adhesion, whereby the shell was permanently attached to some extraneous object, such as the stem of a Crinoid. The two species here figured are interesting for their extraordinarily extensive geographical range—Producta semireticulata (fig. 127, a) being found in the Carboniferous rocks of Britain, the continent of Europe, Central Asia, China, India, Australia, Spitzbergen, and North and South America; whilst P. Longispina (fig. 127, b) has a distribution little if at all less wide.
The higher Mollusca are abundantly represented in the Carboniferous rocks by Bivalves (Lamellibranchs), Univalves (Gasteropoda), Winged-snails (Pteropoda), and Cephalopods. Amongst the Bivalves we may note the great abundance of Scallops (Aviculopecten and other allied forms), together with numerous other types—some of ancient origin, others represented here for the first time. Amongst the Gasteropods, we find the characteristically Palæozoic genera Macrocheilus and Loxonema, the almost exclusively Palæozoic Euomphalus, and the persistent, genus Pleurotomaria; whilst the free-swimming Univalves (Heteropoda)are represented by Bellerophon and Porcellia, and the Pteropoda by the old genus Conularia. With regard to the Carboniferous Univalves, it is also of interest to note here the first appearance of true air-breathing or terrestrial Molluscs, as discovered by Dawson and Bradley in the Coal-measures of Nova Scotia and Illinois. Some of these (Conulus priscus) are true Land-snails, resembling the existing Zonites; whilst others (Pupa vetusta, fig. 128) appear to be generically inseparable from
Fig. 128.—Pupa (Dendropupa) vetusta, a Carboniferous Land-snail from the Coal-measures of Nova Scotia. a, The shell, of the natural size; b, The same, magnified; c, Apex of the shell, enlarged; d, Portion of the surface, enlarged. (After Dawson.) the "Chrysalis-shells" (Pupa) of the present day. All the known forms—three in number—are of small size, and appear to have been local in their distribution or in their preservation. More important, however, than any of the preceding, are the Cephalopoda, represented, as before, exclusively by the chambered shells of the Tetrabranchiates. The older and simpler type of these, with simple plain septa, and mostly a central siphuncle, is represented by the straight conical shells of the ancient genus Orthoceras, and the bow-shaped shells of the equally ancient Cyrtoceras—some of the former attaining a great size. The spirally-curved discoidal shells of the persistent genus Nautilus are also not unknown, and some of these likewise exhibit very considerable dimensions. Lastly, the more complex family of the Ammonitidœ, with lobed or angulated septa, and a dorsally-placed siphuncle (situated on the convex side of the curved shells), now for the first time commences to acquire a considerable prominence. The principal representative of this group is the genus Goniatites (fig. 129), which commenced its existence in the Upper Silurian, is well represented in the Devonian, and attains its maximum here. In this genus, the shell is spirally curved, the septa are strongly lobed or angulated, though not elaborately frilled as in the Ammonites, and the siphuncle is dorsal. In addition to Goniatites, the shells of true Ammonites, so characteristic of the Secondary period, have been described by Dr Waagen as occurring in the Carboniferous rocks of India.
| Fig. 129.—Goniatites (Aganides) Fossœ. Carboniferous Limestone. |
Coming finally to the Vertebrata, we have in the first place to very briefly consider the Carboniferous fishes. These are numerous; but, with the exception of the still dubious "Conodonts," belong wholly to the groups of the Ganoids and the Placoids (including under the former head remains which perhaps are truly referable to the group of the Dipnoi or Mud-fishes). Amongst the Ganoids, the singular buckler-headed fishes of the Upper Silurian and Devonian (Cephalaspidœ) have apparently disappeared; and the principal types of the Carboniferous belong to the groups respectively represented at the present day by the Gar pike (Lepidosteus) of the North American lakes, and the Polypterus of the rivers of Africa. Of the former, the genera Palœoniscus and Amblypterus (fig. 130), with their small rhomboidal and
Fig. 130.—Amblypterus macropterus. enamelled scales, and their strongly unsymmetrical tails, are perhaps the most abundant. Of the latter, the most important are species belonging to the genera Megalichthys and Rhizodus, comprising large fishes, with rhomboidal scales, unsymmetrical ("heterocercal") tails, and powerful conical teeth. These fishes are sometimes said to be "sauroid," from their presenting some Reptilian features in their organisation, and they must have been the scourges of the Carboniferous seas. The remains of Placoid fishes in the Carboniferous strata are very numerous, but consist wholly of teeth and fin-spines, referable to forms more or less closely allied to our existing Port Jackson Sharks, Dog-fishes, and Rays. The teeth are of very various shapes and sizes,—some with sharp, cutting edges (Petalodus, Cladodus, &c.); others in the form of broad crushing plates, adapted, like the teeth of the existing Port Jackson Shark (Cestracion Philippi), for breaking down the hard shells of Molluscs and Crustaceans. Amongst the many kinds of these latter, the teeth of Psammodus and Cochliodus (fig. 131) may be mentioned as specially characteristic. The fin-spines are mostly similar to those so common in the Devonian deposits, consisting of hollow defensive spines implanted in front of the pectoral or other fins, usually slightly curved, often superficially ribbed or sculptured, and not uncommonly serrated or toothed. The genera Ctenacanthus, Gyracanthus, Homacanthus, &c., have been founded for the reception of these defensive weapons, some of which indicate fishes of great size and predaceous habits.
In the Devonian rocks we meet with no other remains of Vertebrated animals save fishes only; but the Carboniferous deposits have yielded remains of the higher group
