Remains of the latter (fig. 123) have been found both in the Old and New Worlds, and indicate the existence in the Carboniferous period of Scorpions differing but very little from existing forms.  The group of the Myriapoda, including the recent Centipedes and Galley-worms, is likewise represented in the Carboniferous strata, but by forms in many respects very unlike any that are known to exist at the present day.  The most interesting of these were obtained by Principal Dawson, along with the bones of Amphibians and the shells of Land-snails, in the sediment filling the hollow trunks of Sigillaria, and they belong to the genera Xylobius (fig. 124) and Archiulus.  Lastly, the true insects are represented by various forms of Beetles (Coleoptera), Orthoptera (such as Cockroaches), and Neuropterous insects resembling those which we have seen to have existed towards the close of the Devonian period.  One of the most remarkable of the latter is a huge May-fly (Haplophlebium Barnesi, fig. 125), with netted wings attaining an expanse of fully seven inches, and therefore much exceeding any existing Ephemerid in point of size.

[Illustration:  Fig. 126.—­Carboniferous Polyzoa. a, Fragment of Polypora dendroides, of the natural size, Ireland; a’ Small portion of the same, enlarged to show the cells; b, Glauconome pulcherrima_, a fragment, of the natural size, Ireland; b’, Portion of the same, enlarged; c, The central screw-like axis of Archimedes Wortheni, of the natural size—­Carboniferous, America; c’, Portion of the exterior of the frond of the same, enlarged; c’’, Portion of the interior of the frond of the same showing the mouths of the cells, enlarged. (After M’Coy and Hall.)]

The lower groups of the Mollusca are abundantly represented in the marine strata of the Carboniferous series by Polyzoans and Brachiopods.  Amongst the former, although a variety of other types are known, the majority still belong to the old group of the “Lace-corals” (Fenestellidoe), some of the characteristic forms of which are here figured (fig. 126).  The graceful netted fronds of Fenestella, Retepora, and Polypora (fig. 126, a) are highly characteristic, as are the slender toothed branches of Glauconome (fig. 126, b).  A more singular form, however, is the curious Archimedes (fig. 126, c), which is so characteristic of the Carboniferous formation of North America.  In this remarkable type, the colony consists of a succession of funnel-shaped fronds, essentially similar to Fenestella in their structure, springing in a continuous spiral from a strong screw-like vertical axis.  The outside of the fronds is simply striated; but the branches exhibit on the interior the mouths of the little cells in which the semi-independent beings composing the colony originally lived.