HKVOMAN AND OLD RED SANDSTONE 8YSTKM 217 



father differenl funt-s, tin- <'<.nilin t -.l tliickneas being still, however, 

 about 5000 feet. 



Middle Devonian. This also comprises two divisions, the 

 Eifdian and the Give'tian. In the former are now placed the 

 Hierges Beds, flagstones and shales, which are subdivided into a 

 lower zone of Spirifer ardutnnensis and an upper zone of Sp. 

 cultrijngatu*. In the basin of Dinant they are some 500 feet 

 thick, and in the basin of Namur they are the lowest beds (with 

 a basal conglomerate). 



The next group is that of the Calceola shales; these are 

 calcareous shales including lenticular beds of limestone which 

 sometimes, as at Nismes and Couvin, swell out to a thickness of 



Coudroz 



I. SECTION THROUGH THE BASINS F NAMI'K AND DINANT 



H. Coal-measures. 

 C. Dinantian. 



D. Up]>er and Middle Devonian. 

 R. Lower Devonian. 



.S. Cambrian and Onlovician. 



300 to 500 feet, hence the group varies greatly in thickness, but 

 has probably an average of 1000 feet Its most characteristic 

 fossils are the little coral Calceola sandalina with Cystiphyllum 

 vesiculosum, Mesophyllum helianthoides, Spirifer specio&us, Meristella 

 plebeia, Phacops Schlotheimi, and Bronteits flabellifer. 



The Give'tian, in its typical locality near Givet, is a mass of dark- 

 grey limestone, over 1200 feet thick, and is specially characterised 

 by certain Brachiopods, viz. Stringocephalus Burtini, Undies 

 gryphus, and Spirifer mediotextits, the bivalve Megalodon cuctillatun, 

 and the Cephalopods Anarcestes cancellatiw, Agoniatitet inconstant, 

 and Orthoceras dolatum. The so-called coral reefs of the Give'tian 

 are merely thick lenticular masses of unstratificd limestone formed 

 by colonies of Stromatoporoids with Favorites, Alveolites, and other 

 corals, such masses being generally surrounded by bedded crinoidal 

 linn-stones or by calcareous shale and limestone. 



Upper Devonian. This is also divisible into two stages, the 

 Frasnian and the Famennian. The former consists of shales and 



