older Deposits of the North of Germany and Belgium. 



255 



thoceras, as well as of certain Trilobites {Homalonotus, Calymene Blumenbachii, &c.), 

 which are undistinguisbable from the known Silurian fossils ; we therefore group it 

 with the upper part of that system*. 



We are aware that objections to this classification may be raised by those who 

 draw their conclusions solely from the organic remains collected under the general 

 name of " Eifel fossils;" among which several species, similar to those that 

 characterize the Strigocephalus limestone of Westphaha and Nassau, are found 

 associated with some of the same forms which occur at Wissenbach. But when 

 analysed, this objection loses its force. In every attempt to define geological 

 subdivisions there must be a difficulty in marking off the lowest beds of one forma- 

 tion from the highest of that which is inferior to it. Those strata, for example, 

 which have scarcely any development in one tract, are frequently found to expand 

 * The fossils of Wissenbach in M. Dannenberg's collection are — 



1. Calymene macrophthalraa. 



1. Ammonites subnautilinus, Schloth. 



2. Noggerathii, Goldf. 



3. latiseptatus, Beyrich. 



4. Dannenbergi, Beyrich. 



'5, compressus, Beyrich. 



(Spirula compressa, Goldf. ^ 

 In the more ample collection of M. Sandemann at Weilburg we observed — 



10. Orthoceras giganteum ? Silurian system. 



.5 

 "a 

 o 

 O 



1. Orthoceras regulare, Schloth. 



2. gracile, Blumenbach. 



1. Patella Neptuni, Goldf, 



1. Isocardia antiqua, Goldf. 



1. Calymene Blumenbachii, Brong. 



2. macrophthalma, Brong. 



3. Homalonotus, probably H. Knightii ? 



4. Hausmanni(Calym.Hausmanni). 



1. Orthoceras regulare, Schloth. 



annulatum, Goldf Large as the 



Silurian species. 

 ■ calamitaceum, Miinster. The same 



variety would seem to occur both in the 



Silurian and Devonian : our O. annulatum. 



dimidiatum ? Silurian system, or 



5. 

 6. 



very near to it. 



gracile, Blum. 



, a large new species identified 



by M. de Verneuil with a species from 



Valogne in France. 



N. S., with oblique septa. 



N. S., with a vertebrated column. 



nodulosum, Schloth. 



11. 



12. 



septa. 



-, large new species with very wide 



■ , a very singular new species, with 



a triangular column or lateral siphuncle, 

 and the angles richly ornamented with 

 raised bosses. 



1. Goniatites subnautilinus. 



Noggerathii. 

 compressus (Spirula 



compressa), 



Goldf 

 , new large species with tubercles in 



two rows. 

 , species slightly differing from G. 



subnautilinus. 

 New species. 



Cyrthoceratites or Lituites, undefined. 

 pyriformis of the Eifel. 



The group of Orthoceratites and Trilobites leave in our minds no doubt that the Wissenbach schists 

 must be considered an upper Silurian deposit. See Plates XXV., XXVII., XXVIII., &c., which have 

 been prepared by M. de Verneuil and M. d'Archiac, and the fossils described by them* 



2 l2 



