396 Dr. Wheelton. Hind ^ John T. Stobbs— 



(xviii) Following the old wagon-way about 600 yards up the dip- 

 slope of the hill from the preceding section, we reach a quarry in the 

 white limestone, at the top of which is a Prodnctiis-hed about 10 feet 

 thick, containing 



Lithostrotion Martini^ E. & H. Prodiictiis giganteus (Mart.). 



Loyisdnleia floriformis (Flera.). P. hemisphcricus (Mart.). 



Syringopora sp. F. scabrieHlo-costatHs, Vaughan MS. 

 Crinoids. 



(xix) Soutli of Holywell, along the eastern margin of Holywell 

 Common, a large number of quarries are being worked in the chert- 

 beds, which here also overlie limestones of the ' Aberdo ' quality. 

 Some of the chert-bands contain ntiraerous crinoidal casts. An old 

 quarry near Pentre Halkyn, where the clierts were to a large extent 

 desilicified, yielded the following fauna : — 



Crinoids. Spiriferina bipUcata, Dav. 



Dielasma hastata (Sow.). Syringothyr'is laniinosa (M'Coy). 



D.Jims. Ostracods. 



Orthotetes crenistria (Ph.\\\.). Delioptychius s^. 



Froductiis longisp'mus, Sow. Fsephodus magnus (M'Coy). 



F. scabriculus (Mart.). A new Crustacean. 

 F. rugatus. 



(xx) Further to the east, near Waenbrodlas, the ' Aberdo ' lime- 

 stones are being worked by most extensive quarries, which are in 

 many respects the most remarkable in the county of Flint. These 

 limestones occur at the same horizon as those at Holloway, Gorsedd, 

 and Trelogan, already described. The photograph (PI. XXII) shows 

 part of the face of the Waenbrodlas quarry, which presents physical 

 features of some interest. A peculiar case of false bedding is here 

 most clearly seen, wliere the edges of one set of thin limestones 

 appear to have been almost planed off in a fiat surface before the 

 deposition of another bed of limestone of singularly uniform thick- 

 ness and persistency. In the uppermost beds of the same quarry, 

 and only partially represented on the right-hand side of PI. XXII, 

 a similar phenomenon may again be observed ; in the latter instance 

 the rate of cutting out of the lower set of limestones is 1 in 13. 

 From the persistent parallelism of the upper and lower surfaces of 

 the individual beds of limestone we infer that these two interrup- 

 tions in the deposition of the strata were not of the nature of 

 current-bedding, but really represent slight unconformities as a 

 result of earth-movement at the time they were laid down, and 

 though here they appear inconsiderable, it is possible that the move- 

 ment at this period produced more striking results in other localities. 

 In this connection we may remember that the 'Aberdo' variety of 

 limestone (which is the kind worked in tliis quarry) is of very local 

 distribution and of very erratic occurrence. The proportion of shale 

 to limestone is extremely variable, increasing from Waenbrodlas to 

 Trelogan, whilst further to the south and west the 'Aberdo' beds are 

 absent altogether. Contemporaneous earth-movement is an easy 

 explanation of this irregularity of deposition, and the secti(m 

 represented in PI. XXII may offer some direct evidence in support 

 of this view. 



