464 J. W. Jackson— 



In the Mitcheldean district, further to the north-east, extensive 

 dolomitization occurs at the same level and continues upwards 

 through the Syringothyris Zone (= C). 



No further information concerning the Chepstow area seems to 

 be available, and the only suggestion that can be made is that the 

 Daviesiella in question came from some portion of the dolomitic 

 series.^ 



In North Wales, according to Davidson (fide D. C. Davies),^ 

 D. llangollensis exists in great plenty in the lower beds of the 

 Carboniferous series at the base of the clifis near Llangollen, and is 

 also found, though not so abundantly, at about the same level at 

 Llanymynech and Porthywaen ; in the Eglwyseg cliffs it lies in a shale 

 bed, from which beautiful specimens of the interior of the ventral 

 valve may be obtained. It is, however, important to notice that the 

 generality of the specimens are so imperfect round the margin as to 

 lead one to imagine that they had been drifted from some distance to 

 the spot where they are at present found. At Llandulas, according 

 to Hind and 'Stobbs,^ it is found some little distance above the 

 base, and associated with Seminula aff. ficoidea. It is thought 

 that these limestones cannot be any lower than the junction of the 

 Seminula and Dihunojjlujllum Zones of Bristol, and the horizon 

 of the Daviesiella is, therefore, regarded as uppermost Sg. 



D. llangollensis is not listed for the Oswestry district by 

 Hind and Stobbs, but it is highly probable that the horizon is 

 the same as in North Wales. Further field-work, however, is 

 necessary in this area, as one would like to know the exact beds 

 from which Ormerod obtained his specimens. The fauna cited 

 by Hind and Stobbs ^ from the Treflach Wood quarries is suggestive 

 of a high horizon in the Dibunophylhcm Zone, in fact D2 ; but no 

 fossils are recorded from the well-bedded, dark limestones at the 

 base of the section studied by them. 



The species is recorded for Anglesey by Dr. E. Greenly,^ who lists 

 it among the fossils referred to the Dj sub-zone, to which he 

 attributes the lowest beds of the island. In his description of the 

 Penmon area he points out that the escarpment at the Careg-onen 

 cliffs is composed of rather dark limestones with shale, and 

 has yielded : Alveolites septosus, Syringopora sp., Daviesiella 

 llangollensis, Spinferina octoplicata ?, and Murchisonia 

 hendalensis.'^ There appears, however, to be some question as to 

 whether the Semimda Zone exists in the island, and it is suggested 



1 In reply to a request from Professor 0. T. Jones, Dr. Sibly writes (22.V.22) : 

 " I do not know Tidenham Chase, but it is extremely probable that the 

 highest Limestone there is of Sg age ; the Dj beds are probably Sandstones." 



2 Davidson, op. cit. (Appendix, 1861), p. 278. 

 = Hind & Stobbs, op. cit., pp. 390 and 498. 



* Hind & Stobbs, op. cit., p. 450. 



5 Greenly, "The Geology of Anglesey" [Mem. Geol. Surv.), vol. ii, 1919, 

 p. 609. 

 '^ Greenly, ibid., p. 652. 



