194: 



DE. WILLS AXD ME. SMITH OX THE LOWEE [vol. Ixxviii, 



which yield this fauna lie not far below the top of the Lower 

 Yalentian. 



It is, however, uncertain whether the upper limit of the Lower 

 Yalentian alwa^^s occurs at the same horizon in these northern 

 outcrops. The summit near Hafod-vr-Abad, for example, is formed 

 b}^ shales which 120 yards east of the house 3delded the following 

 graptolites, indicating the zone of ILonogrcrptiis convolutus : — 



Climacograptus scalaris Hisinger. 

 C tornqv.isti Elles & Wood. 

 Diplograptus (Ortliograptus) hellnlus 



Tornquist. 

 Diplogm2)tus (Mesogro.ptus) magims 



H. Lap worth. 

 Diplograptus (Glyptograptus) tama- 



i-iscus Xicliolson. 



Monograptiis argutus Lapworth. 



M. convolutus Hisinger. 



M. decipiens Tornqiiist. 



M. leptotJieca Lapworth. 



M. lohifenis M'Coy. 



M. regularis Tomqtdst. 



M. sedgicicTii ? Portlock. 



M. undulatus Elles & Wood. 



These are well preserved. The outcrop of the soft shale in 

 which they occur forms a depression which has been taken as a 

 line of division between the L'^pper and the Lower Series. 



On the other hand, at the summit of the Lower Series on the 

 moor road, 400 yards north-east of Bryn-yr-odyn, graptolites in a 

 bad state of preservation were found, which suggest the zone of 

 3T. gregarius. But the reference of the rocks to that zone is not 

 absolutely reliable. The list is as follows : — 



Cliinacograptus rectangularis (?) 



M'Coy. 

 C. tornqnisti Elles & Wood. 

 Diplograptus (^lesograptus) magnus 



H. Lapworth. 



Monograptiis atavus Jones. 



31. gregarixis Lapworth. 



M. rei'olutus Kiirck., var. austenis 



Tornquist. 

 M. triangidatus Harkness. 



One other feature of the Lower Yalentian on Cyrn-y-Brain must 

 be noted : namely, the absence (except at one place) of the speckled 

 variety of mudstone so characteristic of that formation in the 

 other districts. 



Upper Yalentian. 



In the Tarannon Series on Cyrn-y-Brain, the lowest beds are 

 unfossiliferous, except near Llandegla, where at a point 600 yards 

 west of Hafod-Bilston, j]Ionograptus hecki Barrande, M. marri 

 Perner, and AL. runcinatus Lapworth, suggest a horizon about the 

 zone of j\L turriculatus. The presence of the M.-crispus Zone is 

 well established by the follo^ving forms from the roadside 20 yards 

 south-west of the barn at Ty-uchaf, a quarter of a mile south of 

 Bryn-yr-odyn : — 



Monograptiis discus TornqTiist; 



common. 

 M. griestonensis Nicol. 

 M. marri Perner. 



Monograptiis nudiis Lapworth. 

 M. pandiis Lapworth. 

 M. planus Barrande. 

 M. spiralis Geinitz. 



