448 SPECIAL GEOLOGY. 



perforated as in forameniferous shells, or in those which 

 have a siphuncle, like the nautilus. The Bellerophon 

 was long considered to be the shell of a cephalopod, but 

 as it has no septa, it is now classed among the gasteropoda ; 

 it was very prevalent in the carboniferous seas. The 

 plate 299 contains figures of some of the most common 

 shells of this group. The Crustacea were represented in the 

 carboniferous fauna; small CYPEOID^:, belonging to the 

 genera, Cythere, Cypridina, and Cyprella, with Limidus, Apus, 

 and Trilobites are found. Air-breathing articulata have like- 

 wise been obtained; a scorpion was discovered by Count Stern- 

 berg in the coal formation near Prague, which furnishes 

 another proof that, during this epoch, the centre of Europe 

 had a temperature similar to that which characterises the 

 intertropical regions of the present day. Coleopterous 

 insects, belonging to the family Curculionidce and neurop- 

 tera, of the genus Corydale, have been found at Coalbrook 

 Dale, and in Germany several species of orthoptera. The 

 mountain limestone of Bristol has yielded some fine speci- 

 mens of ichthyolites, as the teeth and ichthyodorulites of 

 Placoid fishes ; the heterocercal Lepidoid fishes, as Amllyp- 

 terus and Palteoniscus, and the heterocercal Sauroids, as 

 MegalicJitys and Acrolepis, are found in this formation, with 

 many other families and genera which our limits compel us 

 to omit from the enumeration. 



Professor Yon Dechen found in the coal-field of Saar- 

 briick three species of reptiles referred by Groldfuss to 

 the genus Archegosaurus ; the skulls, teeth, and portions of 

 the skeleton have been found. The true position of these 

 ancient reptiles has not been determined ; they are supposed 

 to be nearly related to the Labyrinthodon; their tegumentary 

 covering consisted of long, narrow, wedge-shaped, tile-like, 

 horny scales, arranged in parallel rows. Footprints of 

 reptiles have been discovered in the coal strata of the 

 United States. 



CAVERNS. The mountain-limestone is remarkable for the 

 extensive caverns which prevail in the strata of some regions, 

 as those of Derbyshire, Devon, Somerset, and various 

 parts of Ireland. Many of these are the channels of 

 subterranean streams, which are conducted into them 

 through fissures in the strata. 



