The Millepedes, like the Land-snails, were first found in the Coal-formation of Nova Scotia, but species have since been discovered not only in Illinois, but also in Great Britain and in Bohemia. In Nova Scotia alone two genera and five distinct species have been found, all in the interior of erect trees, to which these creatures probably resorted for food and shelter (Fig. 126). All the species yet known are allied to the modern Gallyworms, though presenting special features which seem to separate them as a distinct family,[46] and were probably vegetable-feeders. Some of the species have the peculiarity, unknown among their modern successors, of being armed with long spines.[47] The moist, equable climate and exuberant vegetation of the Coal-period would naturally be very favourable to Millepedes, and it is likely that the discoveries made as yet give but a faint idea of their actual abundance. It is not improbable that they subsequently declined, as we know of none between the Carboniferous and the Jurassic, and they do not seem to have improved up to the modern period. The Carnivorous Myriapods, however, or Centipedes proper, a higher and essentially distinct type, are not known until much more recent times. [Illustration: FIG. 126.—Millepedes. From the Coal-formation. _a_, _Xylobius sigillariæ_ (Dawson). _b_, _Archiulus xylobioides_ (Scudder). Anterior segments. Enlarged, _c_, _X. farctus_ (Scudder). Caudal portion. Enlarged.] The insects of the Carboniferous as yet known, belong to three out of the ten or more orders into which the class is divided. One of these is represented by a number of species of Cockroach, another by May-flies and a Dragon-fly, and another by some weevil-like Beetles. The Cockroach is characterised by Huxley as one of the “oldest, least modified, and in many ways most instructive forms of insects;” and both he and Rolleston take its anatomy as typical of that of the class. That these creatures should have abounded in the Coal-period we need not wonder, when we consider the habits of those that infest our houses, and when we further bear in mind the number of species, some of them two inches in length, that exist in tropical climates. So many species of this family have been found in the Coal-formation on both sides of the Atlantic,[48] that we may fairly regard them as constituting one of its most characteristic features, and as probably the oldest representatives of the order to which they belong[49] (Fig. 127). There were also in the Coal-period insects allied to the Locusts and to the Mantids, a carnivorous group. One of the latter (_Lithomantis_), described by Woodward, is a magnificent insect, not unlike some modern tropical species. It was found in the Coal-formation of Scotland. A still larger species, probably the largest insect known, has been described by Brongniart. The May-flies (_Ephemeridæ_) are represented in the Carboniferous by several very large species. That of which the wing is shown in Fig.