262 Professor Sedgwick and Mr. Murchison on the 



The Silurian rocks of this region are, however, distinguished by one organic cha- 

 racter, which has never been observed in deposits of the same age in England. In 

 the Rhenish provinces the remains of land-plants occur at intervals throughout 

 nearly the whole of the ancient series in which any animal remains have been ob- 

 served. From what we had observed in Devonshire, where we found the sandstone 

 rocks beneath the culm-measures to contain plants bearing some analogy to those 

 of the carboniferous epoch, we were led to believe that in extending our researches 

 to distant parts of Europe we might find the equivalents of the Devonian, and per- 

 haps even of the Silurian system, to be also characterized by a Flora as well as by 

 a Fauna. With the development of vegetable forms among the Rhenish rocks we 

 find, as might be expected, traces of carbonaceous matter, one example of which 

 has been noted in our description of the Devonian limestones near Bensberg. In 

 the Aggerthal we again detected thin courses of carbonaceous matter ; and they 

 occurred in the vicinity of sandstone, in which we had observed impressions of 

 stems and leaves. All the ancient rocks on both banks of the Rhine near Bonn are 

 similarly characterized by plants. These forms are generally ill preserved, and 

 have not yet been specifically determined by competent botanists : but it is of the 

 highest interest to make out whether they are, or are not, identical with any species 

 known in the overlying deposits. 



One of the most instructive sections to exhibit the natural relation of the flag- 

 stones, sandstones, and schists, to the Devonian limestones, is seen in passing 

 from Dietz on the Lahn to the baths of Ems. In this traverse we first see an 

 enormous development of glossy slate, flagstones, &c., rising from beneath the 

 limestone of Dietz. These rocks are penetrated by many lead veins, and are in 

 parts much altered by the intrusion of porphyry and basalt ; but the steady dip to 

 the E.S.E., displayed in the rocky cliffs east of Obernhof (though followed by 

 some undulations between that village and Nassau), proves that the whole of this 

 slaty group is interposed between the Dietz limestone with Devonian fossils, and 

 the Silurian shelly grauwacke of the baths of Ems. 



Near the latter place, at Kemmenau and various other quarries, strong beds 

 of quartzose grauwacke, sometimes completely arenaceous and alternating with 

 schists, contain occasionally impure calcareous courses. In these are often found 

 many fossils, which, as a group, are unquestionably Silurian. Among them we 

 collected three species of Homalonotus, one of which approaches in character the 

 H. Knightii, and we shall hereafter notice them as occurring in the flagstones of 

 the Ahr, at Martelange, &c., on the left bank of the Rhine ; another is what the 

 Germans have published as Asaphus Hausmanni, and a third is largely tuberculated 

 on the body like Homalonotus Herschelii, Sil. Syst. The same forms of Trilobite 

 occur in the grauwacke which rises from beneath the slates of Wissenbach. These 



