Vol. 62.] ROCK'S OF WESTERN" CAERMA.RTHENSHIEE. 617 



Some bands are crowded with graptolites. Trilobites also are fairly 

 numerous. The following fossils occur : — 



Didymograptus bifidus, Hall. 

 Didymograptus Nicholsoni, Lapw. 

 Didymograptus Nicholsoni var. 



planus, Elles & Wood. 

 Didymograptus affinis, Nicb. 

 Didymograptus acutidens, Lapw. 

 Diplograptus dentatus, Brongn. 

 Climacograptus tereliuscitlus, His. 

 Climacograptus confertus, Lapw. 



Dhacops llanvimensis, Hicks. 

 Barrandca Homfrayi, Hicks. 

 JEglina sp. 



Illcenus Hicghesii, Hicks. 

 JPlacoparia cambrensis, Hicks. 

 Calymene parvifrons, Salt. 

 Ophileta. 

 Bellerophon ; etc. 



(2) The Northern Outcrops. — The Didgmograptus-bifidus 

 Beds on the north of the anticline differ lithologically, to some 

 extent, from their equivalents on the south, and (taken altogether) 

 they are not so fossiliferous. Having been affected more or less 

 by cleavage, the fossils that do occur are neither so easy to find 

 nor so well preserved. 



On entering the district on the east, the first or main outcrop 

 extends from Melin-ricket to a point about a quarter of a mile 

 south of Pont-gowyn ; and, on reaching the Tave, it occupies the 

 ground between Login and Llanglydwen, a distance of about 

 3| miles. 



Didgmograptus bifidus, Hall, occurs in a small quarry near 

 Penrhiw (Thomas lioberts's v Penllwyn-bach '" locality). Several 

 little quarries have been opened here in one of the ash-bands. 

 D. bifidus has also been collected at Pantglas and Pantybrodyr. 



The ground between the Cywyn and the Dewi-fawr has been 

 much cut up by faults which go on splitting westward. This is 

 well shown by the behaviour of the ash-bands (see PL XLVI, map). 



The road between Plas-parcau and Mydrim affords an almost 

 continuous section across the beds, showing much of their intricate 

 plication. , Dips here change their inclination and direction at very 

 frequent intervals. The mudstones at Plas-parcau Quarry have 

 yielded a fair number of graptolites, including Didymograptus 

 bifidus, Hall ; D. Murchisoni, var. geminus, His. (or a large 

 D. bifidus) ; D. cf. hirundo (?), Salt., etc. There is some obscure 

 faulting in the immediate neighbourhood of this quarry; and, 

 weighing the evidence of the fossils, it may be questioned whether 

 the succession is normal here. 



Fossils have also been collected from a roadside section near 

 Penycoed, where D. bifidus, Hall, D. Murchisoni (?), Beck, and a 

 several-branched form of graptolite occur. The graptolite-bearing 

 rock here is quite different in character from the usual type of 

 D.-bifidus Beds, consisting of thin, hard, flaggy, striped bauds 

 -embedded in black shales. There is a complication of faults here 

 again, and these beds may not be in their right place, for between 

 this section and the true base of the D -Murchisoni Beds, a little 

 farther north, some indisputable D.-bifidus mudstones occur. 



D. bifidus occurs in Penwch farmyard, and near Salem Chapel. 



