Vol. 62.] ROCKS OP WESTERN CARMARTHENSHIRE. 



631 



Dyffryn. At Wern-y-berni they are thrown northwards by some 

 obscure faulting, and are well seen at Sarnau, Cwrtau-mawr, and 

 Cwrtau-bach. The cut-up character of the ground west of Cwrtau- 

 bach and round Llwyn-llwyd and Lan affords abundant exposures, 

 but it is often very difficult to trace the relation between the various 

 beds. The road near Tycoed and Waungron affords a continuous 

 exposure, but fossils are obscured by cleavage. South of Abertigan 

 the beds run out in a manner similar to that observed west of 

 Frowen. On the north the beds are faulted against Didymograptus- 

 Murchisoni Flags. 



Another belt of these beds follows the Llanglyd wen- Abertigan 

 outcrop of AsapJms-Be&s, and, like them, is cut off by a fault near 

 Fron-isaf. 



(/3) Calcareousband s. — It is suspected that there is a calcareous 

 development of the buff-yellow weathering mudstones at more than 

 one horizon ; but it is quite clear that the most persistent of them 

 is very local. Whether this is due to conditions of sedimentation, 

 or to subsequent weathering and decalcification, has not been made 

 out. 



At the village of Mydrim there is a considerable thickness of 

 calcareous beds, some lenticular bands being fairly- compact blue- 

 black limestone. A good section of the beds is seen under the 

 graveyard, and fossils are abundant : some bands are crowded with 

 graptolites of types hitherto unknown elsewhere in South Wales. 

 The following have been identified : — 



Leptograptus validus, Lapw. 

 Leptograptus grandis, Lapw. 

 Leptograptus latus, Elles & Wood. 

 Dicellograptus cf. sextans, Hall. 

 Dicranoqraptus brevicaulis, Elles & 



Wood. 

 Dicranograptusci. Nicholsoni, Hopk. 

 Dicranograptus rectus, Hopk. 

 Dicranograptus^ sp. (new). 



Diplograptus cf. foliaceus, Murch. 

 Didymograptus superstes, Lapw. 

 Climacograptus sp. 

 Glossogrcvptus (?) HincJcsii, Hopk. 

 Dictgograptus sp. 

 Trinucleus faints, Salt. 

 Trinucleus sp. 

 Orthis testudinaria, Dalra. ; etc. 



Eastward, these beds are only traceable for a short distance, but 

 westward they are more persistent. 



A well has recently been sunk at Oernant-uchaf, cutting through 

 most of these beds, and the material brought up has yielded fossils 

 of the above description and, in addition, two or three poor specimens 

 of Nemagraptus gracilis, Hall. 



At Castell-gorfod the beds have been quarried for lime-burning ; 

 but it does not appear that the experiment was attended with much 

 success. 



The beds occur at Penlan, but the limestone is very thin. It does 

 not come to the surface at all between here and Llain, where an 

 occasional slab occurs among the black shales. The same beds are 

 seen in a deep ditch immediately west of Trebleiddiau ; but they 

 are exceedingly rotten, yielding only an occasional slab of compact 



Q. J. G. S. No. 248. 2 x 



