Vol. 56.] SHALES OF THE WELSH BORDERLAND. 37-S 



Cardiola interrupts Brod., Chonetes minima, Sow., and several 

 other small brachiopoda occur. 1 



The higher beds of this zone, which, as I have said, are more flaggy 

 than those just mentioned, are well exposed at Trecoed beside the 

 track leading from the high road to the Farm, in the old quarry 

 north of Llanelwedd Hall, and in the bed of the Wye. 



At Trecoed the C.-Murchisoni zone has yielded the graptolites 

 enumerated in Table I, col. B (p. 378). Specimens of Acidaspis 

 Prevosti( = Hughesi?), Cardiola inter rupta, and other small brachio- 

 poda are also abundant. 



In the old quarry north of Llanelwedd Hall the beds dip at 35°, 

 S. 30° E. ; they overlap on to the Llandeilo rocks and yield the 

 graptolite-fauna recorded in Table I, col. C. Other fossils found 

 here include Acidaspis Prevosti, Orthoceras sp., Glassina Iceviuseula 

 (Sow.), Atrypina Barrandei, Dav. ?, A. reticularis, Linn, (young), 

 and Lingula Symondsi, Salt. ? 



The fauna at these two localities is very similar to that which 

 occurs at Pencerrig, but C. Murchisoni is not so abundant r 

 and Retiolites Geinitzianus is absent. Specimens of Monograptus 

 riccartonensis are occasionally met with in the highest horizons at 

 these localities, indicating the coming in of the fossil which attains 

 its maximum development in the succeeding beds. The beds of the 

 -Murchisoni zone which contain M. riccartonensis must be regarded 

 as the highest belonging to that zone, and at Trecoed they are 

 succeeded, within a very short distance, by beds in which M. riccar- 

 tonensis is almost the only fossil found. 



In the bed of the Wye I was able to obtain only Cyrtograptus 

 Murchisoni and Monograptus vomerinus (Nich.) var. a. 



(2) Zone of Monograptus riccartonensis, Lapw. — The 

 beds which succeed those containing Cyrtograptus Murchisoni as. 

 the predominant form are characterized by the abundance of 

 M. riccartonensis. This graptolite often occurs to the exclusion of 

 almost every other form, though it is not so abundant in the 

 Builth district as in some other areas. These beds do not differ 

 in any important lithological character from the highest horizons of 

 the underlying zone, but the fauna is sufficiently distinct to mark 

 them off. 



The beds are exposed for a thickness of about 12 feet in the 

 lower part of an old quarry behind Castle Crab Farm. They 

 consist of hard, grey, calcareous flagstones, often breaking with a 

 splintery fracture. The fossils are seen to occur in bands, though 

 there appears to be little or no difference in the lithological 

 character of these bands, and there is no difference in the fauna 

 that they contain. The fauna found here includes that enumerated 

 in Table I, col. F 1 (p. 378). Orthoceras sp. is also abundant. 



The coming in of Monograptus dubius, Suess, is characteristic of 



1 I have to express my best thanks to Mr. F. E. C. Eeed for kindly naming 

 the brachiopoda mentioned in this paper. 



