This Order is represented by a single fossil (Fig. 45), discovered in the coal at Mazon Creek, Illinois, America, by Meek and Worth. It differs greatly from any of those in existence at the present day. The body is cylindrical, and composed of ten segments. The cephalic appendages (that is, the antennae and mouth parts) are inserted into a single unsegmented cephalic mass (the head). Each segment behind the head bears a single dorsal and ventral plate of equal breadth and length. The limbs are placed in these plates with a wide space between the base of each leg and that of the opposite one of the pair. Along the back, bundles of bristles are arranged in longitudinal rows. ORDER II. CHILOPODA. The fossil forms of this Order resemble those of the Chilopoda of the present day. The oldest of them are found in amber. The following families have been found:— _Lithobiidae._ Several species have been found in amber. _Scolopendridae._ One species in amber, several species in later Tertiary formations. _Geophilidae._ Three species in amber. Two species resembling the Schizotarsia of the present day have been found in amber. {76}ORDER III. ARCHIPOLYPODA. The most numerous of the fossil families. With a few exceptions, all the Palaeozoic (that is, the oldest) Myriapods belong to this Order. The Carboniferous Archipolypoda seem to be much more numerous in the coal of America than in that of England. They resemble for the most part the Myriapods of the present day, except that all the segments without exception bear legs. The families are three in number. Family 1. _Archidesmidae._ Resemble the _Polydesmidae_ of the present day. Two species have been found by Page in the Old Red Sandstone of Forfarshire. He named them _Kampecaris_. One found by Peach in the same formation is called _Archidesmus_. Family 2. _Euphoberiidae._ They show some resemblance to the _Julidae_ of the present day, but the dorsal scutes, or plates of the back, are more or less perfectly divided into two divisions corresponding with the pairs of legs. The following are the principal fossils of this family:— _Acantherpestes._ Found by Meek and Worth in the coal at Mazon Creek in America (Fig. 46). _Euphoberia._ About 12 species found at the same place as the last named. _Amylispes._ Found by Scudder, Mazon Creek, America. _Eileticus._ Scudder, Mazon Creek, America. Family 3. _Archijulidae._ The dorsal plates nearly consolidated, but the division still apparent. Fossil forms are— _Trichijulus._ Scudder, Mazon Creek, America. _Xylobius._ Dawson. Found in the coal in Nova Scotia. Two species found at Mazon Creek, America. ORDER IV. CHILOGNATHA. Families corresponding to those of the present day. The oldest specimens come from the chalk in Greenland; most of the others from amber. Family 1. _Glomeridae._ One form, _G. denticulata_, has been found in amber.