Geology of the Harz Mountains. 213 



that the graptolites do not occur in the lowest beds, but are 

 found at the very top of the Hercynian series. Might I 

 suggest the possibility of these graptolites having migrated 

 as a colony from some other area during the deposition of 

 this formation? In our Scottish Old Eed Sandstone of 

 Lanarkshire a similar case occurs in the shape of a single 

 graptolite found in a thin band of shale about 5000 feet 

 above the base of the system.^ 



The granular diabase generally associated with the Upper 

 Hercynian strata, is noticed under the palaeozoic volcanic 

 rocks at p. 244. 



6. Devonian. 



The Devonian rocks rest conformably on the Hercynian, 

 and are, on the Harz, as at other places in Europe, palaeon- 

 tologically divisible into three groups — (1.) Lower, (2.) 

 Middle, and (3.) Upper. 



(1.) The Lower Devonian rocks of the Harz are of two 

 facies — the " Upper Harz facies " and the " Lower Harz 

 facies." 



The Upper Harz facies is represented (1st) by a set of 

 apparently unfossiUferous quartzites, forming the Bruch- 

 berg, a high ridge running from the Brocken south-west- 

 wards to the edge of the Harz near Osterode ; and (2d) by 

 a series of fossiliferous sandstones, well developed, between 

 Clausthal, Goslar, and Ocker, where they form the Eam- 

 melsberg, Bocksberg, Kahleberg, etc. This rock is named 

 the " Spiriferensandstein," from the numbers of spirifers it 

 contains. 



The fossils which characterise the Spiriferensandstein are : ^ 



Ctenocrinits decadactylus. Rhynchonella Orhignyana. 



Cyathocrinus piuTiMus. Pterinea fasciculata. 



Tentactulites scalaris. Nucula Krachtae. 



Spirifer macropterus. N. securiformis. 



S. cuUrijiigatits. Cardinia Vetusta. 



S. speciosus. Orthoceras planiseptatum. 



S. eurvatus. Phacops latifrons. 



Chonetes sardnulata. Homalorvotus Gigas. 



C. dilatata. Etc., etc., etc. 



1 A. Geikie, Text-book of Geology, p. 714. 



* V. Groddeck, Abriss der Geognosie des Harzes, 2d edit, p. 91. 



