Vol. 56.] WENL0CK SHALES OF THE WELSH BORDERLAND. 



391 



The highest beds of the zone are seen in a small quarry on the 

 right bank of a small tributary stream coming in from Glyn : these 

 again yielded M. dubius and M. Flemingii (Table III, col. L) ; and 

 similar beds occur on the right bank of the main stream, just after 

 it is joined by this tributary (Table III, col. M). These beds are 

 immediately succeeded in the main stream by a series of bluish-grey 

 calcareous shales (loc. 18, fig. 5, p. 388), in which a colonus-like 

 form is the predominant graptolite. They must be regarded, 

 therefore, as the base of the Ludlow Series ; they gradually give 

 place upwards to beds in which M. colonus, M. bohemicus, and 

 M. Nilssoni can be recognized. 



(Ab) Section near Dingle Mill. 



Zone of C yrtograjptus Lundgreni, Tullb. — This zone is 

 exposed in the railway-cutting west of Middletown Farm, on each 

 side of the bridge over which the road runs towards Llwyn-y-melin. 

 The rocks consist of the typical bluish-grey shales and flags ; they 



Pig. 6. 



^p&$^ \Railwav-mttini? 



a {j fZone of Cyrt.rigidus 



Zone of Cyrt. Lundgreni 



L r Ludlow 



Ucheldre 



dip S. 10° E. at 45°, and have yielded C. Lundgreni, Monograptus 

 Flemingii var. y, and M. dubius. 



The upper beds of the zone are exposed in the lane leading to 

 Dingle Mill, and in the bed of the stream which runs past the Mill. 

 They have yielded abundant forms of M. dubius and a few fragments 

 of M . Flemingii, probably var. 3. 



There is no further exposure till near Upper Heldre, where the 

 rocks contain an undoubted Lower Ludlow fauna. 



