1876-1877-] 255 



being filled with masses of flint gravel or rather breccia of flints 

 and light grey calcareous clay, derived from the waste of the chalk 

 itself; some of the flints are red, others yellow, or banded with 

 yellow and red, the deepest tint of red being always in the very 

 heart of the flint. This flint breccia is well seen at the quarries 

 at the Black Mountain, near Windy Gap, but it is not found at 

 any other place along the escarpment of the Black Mountain. 



Owing to their varied composition, the great number of fossils 

 contained, and the fact of it being the locality where the richest 

 and most complete section of Upper Greensand beds are found, 

 the Cretaceous rocks of the Black Mountain are the most interest- 

 ing rocks of this formation occurring in Ireland. The section so 

 well exposed for examination in the rocky gorge of Colin Glen 

 we give in detail, as an index to the other localities, and in order 

 to show the nature and composition of the various sub-divisions. 

 A list is appended of the characteristic fossils occurring in the 

 strata exposed at the various sections seen along the escarpment 

 so far as the Crow Glen. 



SECTION IN COLIN GLEN. 



No. of Thickness 



Beds. in Feet. 



i .a. Hard white chalk, thin bedded; and with flint, nodules ' 



occurring irregularly. Fossils not plentiful - -60 



Belemintella mucronata Rhynchonella octoplicata 

 Lima Hoperi „ plicatilis 



Pecten cretosus Magas pumilia 



Ananchytes ovatus Parasmilia centralis 



cldaris sp. cceloptychium furcatum 



Spondylus spinosus Paramoudra Bucklandi " 



Terebratula carnea Amorphospongia 



i.b. Hard white chalk, in thicker beds, and the flints in 

 regular rows about 18 inches apart on an average. 

 The Fossils are not at all plentiful - - -140 



