SILURIAN 8Y8TKM 185 



F, has until recently been regarded as Devonian by German 

 geologists, but the most recent study of the beds and their contents, 

 by F. Seeniann, 25 has shown that it is more intimately connected, 

 both stratigraphically and faunally, with the top of Stage E than 

 with the beds above. Thus it contains graptolites, Mon. colonus, 

 M. priodon, Callograptiis dichotomies, and others, with Orthoceras 

 subannukire and other species, and lastly, no Goniatites have been 

 found in it Seemann, therefore, regards this black limestone 

 (Fj) as the top of the Silurian Series, and as forming to some 

 extent a passage from the Silurian to the Devonian. It is, how- 

 ever, clearly marked off from the overlying white and red lime- 

 stones which, in his opinion, form the base of the Devonian System 

 (see p. 222). 



The fauna of the thick mass of limestone forming Stage E is a 

 very large one, including no fewer than 183 species of trilobitea 

 belonging to the genera Acidaspis, Arethusina, Phacops, Proetus, 

 Illtenus, Lichas, Cyphaspis, Cheirurus, Spharexochus, etc. Of 

 Orthoceras there are 250 species, and of Cyrtoceras, 150. Lamelli- 

 branchs are very numerous, and include the genera Dualina (100 

 sp.), Panenka (84 sp.), Cardiola (65 sp.), Lunulicarditim (85 sp.), 

 Paracardium, Prcecardium, Kralovna, Pterincea, Vlasta, Redonia, 

 and Prcehicina. 



4. Germany 



In Thuringia there is again a normal succession up to a zone of 

 Mon. colonus, above which there appears to be a break in the 

 sequence ; and in the Kellerwald the case is similar, but there 

 shales with Cardiola interrupta, Monograptus, and Cyrtograptus are 

 succeeded by beds with Phacops, Harpes, and Hercynella before 

 they are cut off by the unconformity. 



In the Hartz Mountains, however, the stratigraphy is very 

 different. There the oldest rocks exposed are a thick series of 

 grits, mudstones, and shales, with some limestones which seemed to 

 contain a mixed fauna of Silurian and Devonian forms with 

 graptolites. By Beyrich and Lessen they were called the Hercynian 

 and were regarded as an intermediate series between the Silurian 

 and the Devonian Systems, but recent researches have shown that 

 the central core of the range is a dislocated and faulted mass or com- 

 plex, and that large parts of it are really Silurian while others are 

 Devonian. To the Silurian must be referred the greywacke of 

 Tanne, and the black limestones of the Tannenthal, which contain 

 Cardiola interrupta, as well as the Monograptus slates of Wieda ; 

 though these seem to overlie beds with Devonian fossils, and were 

 formerly regarded as the highest member of the series. 



