CAEBONIFEKOUS FATJlirA. 151 



inches, nearly equal to the expanse of the largest of the living 

 dragoD -flies, to which it appears to have been related. The Car- 

 boniferous Arachnida comprise representatives of true spiders (Pro- 

 tolycosa, Anthracomartus), scorpions (Eoscorpius, Cyclophthalmus), 

 and pseudo-scorpions (Microlabis). The scorpions appear to have 

 attained a degree of specialisation very little below that of their 

 modern representatives ; but the true arachnids have all, or nearly 

 all, segmented abdomens, and may be considered to mark a transi- 

 tion between the arthrogastric and anarthrogastric forms. The 

 Myriapoda, which have a solitary forerunner in the Devonian rocks 

 of Scotland (Forfarshire), are represented by both the cheilognath- 

 ous and cheilopodous types, although on account of certain structu- 

 ral peculiarities the greater number of these earlier forms (Eupho- 

 beria, Xylobius, Trichiulus) have been constituted into a special 

 order, the Archipolypoda. 



Of the remaining invertebrate fauna of the Carboniferous period 

 little need be said. The various groups of the tabulate and rugose 

 corals CLithostrotion, Syiingopora, Cyathophyllum, Amplexus, Za- 

 phrentis), the braohiopods, pteropods, lamellibranchs, gasteropods, 

 and cephalopods, among the mollusks, and the crinoids and blas- 

 toids (Actiaocrinus, Platycrinus, Cyathocrinus, Dorycrinus, Batto- 

 crinus, Pentremites, Gtranatocrinus) of the Echinodermata, have, 

 as in the Devonian formation, abundant representatives; but they 

 belong in considerable part to genera which now appear for the 

 first time, or to such as had but a feeble development hereto- 

 fore. The widely distributed group of trilobites, which, as has al- 

 ready been seen, played such an important part in the faunas, 

 of the Cambrian and Silurian periods, has here barely four gen- 

 eric representatives, Phillipsia, Proetus, Griffithides, and Bra- 

 chymetopus, whose species occur in the main part in the deposits 

 situated below the true coal.* With these forms the trilobites 

 disappear forever from the scene. While the deposits of the pre- 

 ceding Silurian and Devonian formations have shown a fair repre- 

 sentation of at least two of the primary groups of the Echinoder- 

 mata, the Asteroidea and Crinoidea, especially of the latter, it is 

 not until the present period that the urchins themselves (Echinoidea) 

 acquire any signiflcance (Archseocidaris, Palechinus, Melonites); 



* Professor Clay pole has latterly aunoutioecl the discovery of Dalmania in 

 t.lie "Wavei'ly group" (Lower Carboniferoas) of Ohio. ' 



