complex family of the Ammonitidoe, 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.

[Illustration:  Fig. 129.—­Goniatites (Aganides) Fossoe.  Carboniferous Limestone.]

[Illustration:  Fig. 130.—­Amblypterus macropterus.  Carboniferous.]

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 (Cephalaspidoe) 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 Paloeoniscus and Amblypterus (fig. 130), with their small rhomboidal and 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