The Carho)iiferous Succession heloiv the Coal-Measures. 457 



L. Portlochi (Bronn), and frequently with Lonsdaleia rugosa, M'Coy, 

 and Phillipsastroia radtata, E. & H. It differs somewhat from the 

 typical C. reginm from the Bristol area. 



Dibunophyllum. Corals belongin<2^ to this genus are distributed 

 through the whole series of the Carboniferous Limestone of North 

 Wales, with the possible exception of the lowest of these or the 

 Seminula ficoides zone. 



Lithostrotion Martini, E. & H. This coral appears to characterise 

 those limestones that occupy an intermediate position, and it has 

 therefore a moderate range, extending from the base of Cyathophyllum 

 Murchisoni zone, as seen at Bvvlch-y-gwynt and near Llanferres, to 

 beds 300 feet higher in the series at Pot Holes, in the White 

 Limestone on Holywell Common above the Grange Quarry (see 

 section, Fig. 1, p. 394), at Gwaenysgor, and in the White Limestone 

 overlying the Brown Limestone of the Eglwyseg ridge. 



Lithostrotion irregidare (Phill.), L. Portlocki (Bronn), L. jnnceum 

 (Flem.). These species are found most abundantly in beds which 

 form the uppermost 100 feet of the Carboniferous Limestone of this 

 district, as exposed at Hendre, Gwernymynydd, Pot Holes, Minera, 

 Ty-nant ravine, Corwen, and Treflach Wood Quarries ; they are 

 thus seen to be widely distributed. 



Calophjllum 9, Campophyllum Murchisoni, ClisiophylJum Curkeenensis. 

 These three corals are not very abundant, and have only been found 

 in the upper beds of limestone occurring at Waenbrodlas, near 

 Gwyndy, and at Treflach Wood Quarries. 



Spirifer triangularis (Mart.), S. trigonalis (Mart), d'Orb. These 

 Brachiopods practically make up whole beds in quarries at Gwerny- 

 mynydd and north of Gwyndy, at an estimated distance of 100 feet 

 from the top of the limestone. 



Productus longispinus, Sow. This is abundant in the uppermost 

 beds only of the limestone, such as the Aberdo Limestone horizon, 

 and it extends into the cherts at Gronant. 



Amplexi-zaphrentis. This genus is fairly abundant in the upper 

 portion of the limestone, and has a wide distribution. 



Clisiophylhim afif. Curkeenensis, Vaughan, Calophyllum 0, Vaughan. 

 These two species of Corals have only been found near the top of 

 ithe limestone, and are more restricted than Productus longispimis, Sow. 



Productus giganteus (Mart.). These large Brachiopods are very 

 abundant in the top beds of the limestone ; after a distance of 

 100 feet from the top they are of sparing occurrence, and are not 

 met with in those beds where P. Cora, d'Orb., and P. hemisphericus 

 are so abundant near the base of Cyathophyllum Murchisoni zone. 



By analysis of the fossil lists, then, we are enabled to correlate, 

 with varying degrees of precision, the different exposures of the 

 Carboniferous Limestone in this part of North Wales. In ascending 

 order, the localities affording sections in the same horizons may thus 

 be summarised : — 



1. The lowest limestones at Llandulas ; Pentre - bach, near 

 Dyserth ; and Eglwyseg ridge, near Dibrun Uchaf. Characteristic 

 fossils: Seminula ficoides, Daviesiella Zlangollensis. 



