13S DE. Ct. l. eiles OS THE eala corA'TEY : _Tol. Ixxviii, 



rather softer than those at a higher horizon, and have Yielded a few 

 graptolites (see p. 1^) : but elsewhere no ti-aces of any organism 

 haYe been found, althouofh the shales are masrnificentlY displaYed 

 along the course of the Xant-hir llowing down from the slopes of 

 Ai'enig across their stiike. The shales appear to roll somewhat, 

 and one marked fold bi-ings up the Yolcaiiic rocks again : they may 

 also be repeated to some extent by stiike-faulting. although in the 

 absence of fossils the magnitude of such repetition cannot be 

 estimated: they are probably affected to some extent by tear-faults, 

 but again the degree of this is difficult to detect in the absence of 

 any clue as to the relatiYe age of the beds, and owing to the fact 

 that they are widely concealed beneath a tract of heathery moor- 

 land. Towards their upper limit the shales again become some- 

 what softer, but at this horizon beds of hard sandy mudstone 

 begin to be intercalated anione them : these gradually increase in 

 number and importance, until they pass OYer into a definite series 

 of fine massiYely-bedded sandstones containing an appreciable 

 quantity of mica. 



Cxlyn-CTOwer Beds. 



This series is well exposed in many places, especially in Glyn 

 Gower, probably by reason of its nature, and is distinsruished by 

 its hardness and widely-separated bedding-planes ; the coarser beds 

 gradually giYC place upwards to bands of finer texture, of the 

 nature of sandy mudstones. These not only contain sonoie shale- 

 bands, but also a certain amount of calcareous material in the form 

 of concretions of all sizes ; the commonest of these concretions are 

 about the size of a man's head : in places. howeYer, where they haYe 

 been worked for lime (as on Bryniau Goleu) they are considei-ably 

 larger. The shale-bands as a rule are somewhat cleaYed, although 

 the cleaYage rarely is sufficiently well-deYeloped to obliterate the 

 bedding. It is in these sandy mudstones that the lowest ash- 

 bed occurs. Although the beds immediately aboYe and below the 

 ash are'YerY much alike. Yet. taking them as a whole, a marked 

 difference may be noted in the lower beds both in general litho- 

 logical characters and in their fossiliferous nature, so that they 

 may be conYcniently separated off as constituting a series by them- 

 selYes, the Glyn-G-ower Beds. These deposits are but sparsely 

 fossiliferous. and, although the fauna is CYcrywhere meagre and 

 lacks the Yariety of the higher beds, yet it is not wholly dcYoid of 

 interest. In the black shales occuning in the sandy mudstones 

 graptolites haYe been found {Ortliograpius f 'run cat us), and the 

 bedding-planes of the massiYely-bedded sandy mudstones are occa- 

 sionally coYered with FJecfamlGnifes sericea — in fact, this fossil, 

 together with Glyptocri'/ius hasalis, is so much the commonest 

 organism found that (from the palseontological point of Yiew) the 

 series might well be teiTQed the FJectamho'nites-seri ceo. 

 Beds. 



