526 HISTORICAL PALAEONTOLOGY. 



poses upon a sandy shale or clay, which is known as the 

 "underclay" or "floor" of the coal, and through which spread 

 numerous fossils referred to the genus Stigmaria, and now 

 known to be the roots of plants (Sigillaria). Each seam is 

 also surmounted by a bed of shale, forming the so-called 

 " roof" of the coal, and in this are found numerous flattened 

 and compressed branches and stems of plants. 



LIFE OF THE PERIOD. The vegetation of the Carboniferous 

 period is exceedingly luxuriant ; but its characters have been 

 already so fully discussed as to render unnecessary anything 

 further here than a mere allusion to its chief members. The 

 chief feature in the Carboniferous flora is the great predominance 

 of Cryptogams as compared with Phanerogams. The former 

 are amply represented by numerous Ferns, Calamites, Lepido- 

 dendroids, and, perhaps, Sigillarioids. The latter, with few 

 exceptions, are represented only by Gymnospermous Exogens. 



The Protozoa are represented in the Carboniferous rocks by 

 a few Sponges and by the shells of Foraminifera, of which the 

 genus Fusulina (fig. 1 1 ) is the most characteristic. The tests 

 of this form are sometimes so abundant as almost to make up 

 the whole of certain limestones. 



The Cceletiterates are represented almost exclusively by 

 Corals, which abound especially in some of the limestones of 

 the Lower Carboniferous series. Most of the Carbonifer- 

 ous Corals belong to the Tabulate division of the Zoantharia 

 Sderodermata, or to the Rugosa, and amongst the more impor- 

 tant genera may be mentioned Lithostrotion, Syringopora, Lons- 

 daleia, Cyathophyllum, Amplexus, Farosites, and Chatties, 



Of the Echinodcrmata the most abundant are the Crinoids, 

 which occur in vast profusion in most of the limestones of the 

 Carboniferous series. The most important genera are Aetino- 

 crimts, Platycrinus, Cyathocrinus, Poleriocrinus, and Rhodocri- 

 nus. In some parts of the Carboniferous, Pentremites are also 

 exceedingly abundant. Lastly, the Echinoids are represented 

 by the two aberrant genera, Archceocidaris and Palcechinus, 



Annelides are not abundant, with the single exception of 

 the little Spirorbis, pr Microconchus, earbonarius, which some- 

 times occurs in great plenty. The Crustaceans belong chiefly 

 to the groups of the Ostracoda and Phyllopoda. The Trilo- 

 bites make here their last appearance ; the genera Phittipsia, 

 Griffithides, and Brachymetopus, being the last of the race. 

 The Eurypterids also appear to die out finally in the Carbon- 

 iferous. On the other hand, the Xiphosura are now repre- 

 sented by the genera Bdinurns and Preslwichia (fig. 119); and 

 the Macrourous Decapods appear to commence their existence 



