Davidson — Earliest British Brachiopoda, 307 



to be very scarce, but the beds are mucli cleaved, and the colour 

 is not in any way favourable to the exhibition of the characters 

 of so thin a shell. L. ferruginea is a small shell, rarely much ex- 

 ceeding two and a half lines in length by some two in width. In 

 external shape it is ovate, oblong, widest about the middle, broadly 

 rounded in front, sides nearly parallel for some distance, while the 

 beak is obtusely pointed. The valves are also very slightly convex, 

 and marked with concentric lines of growth. 



After an attentive comparison of the single example of the variety 

 ovalis with a number of specimens of L. ferruginea from the ' Mene- 

 vian Group,' I was quite at a loss to make out any distinctive features, 

 and I find that Mr. Salter himself does not fail to observe that his 

 variety is not to be distinguished from the other, ''except by the 

 front of the front edge, which is rounded off and not squared at all." 

 However, this last character cannot be considered of any importance, 

 for I have specimens before me of a similar size of L. ferruginea, 

 which have the front quite as much rounded off as is seen to be the 

 case in the single example of the var. ovalis. There can also be no 

 doubt as to the shell originally termed unguiculus (in 1865), being 

 the same species as the L. ferruginea described in 1867. L. ferruginea, 

 it is true, like most of its congeners, varies slightly in its shape in 

 different examples ; some, therefore, have their front a little more 

 rounded than others, and the posterior portion converges rather more 

 in some individuals than it does in others. After a very minute study 

 of a number of specimens submitted to my examination by Messrs. 

 Hicks and Belt, it appeared to me that the shell under description 

 made its first appearance in the lowest beds of the Harlech period, 

 and continued to live during the whole of the 'Menevian' or 'Lower 

 Lingula flags,' and was very probably, if not certainly still existing, 

 during the period of the deposition of the Middle and Upper Lingula 

 flags ; for several examples much resembling Salter's species were 

 met with by Mr. Belt in his ' Dolgelly and other divisions (?).' This, 

 however, must still remain an undecided question, for several speci- 

 mens of L. Icepis can hardly be distinguished from L. ferruginea, and 

 in this predicament we find the small specimen found by Mr. Hicks 

 at Rhyw-felyn, near Mawddach, North Wales (PL XV. Fig. 7). L. 

 ferruginea occurs in the ' Menevian ' rocks of St. Davids, as well as 

 at Camlan, Tafern Helig, Waterfall Valley, near Maentwrog, and 

 several other places in North Wales, also in the Harlech grits of 

 Solva and St. David's. 



3. LiNGULELLA L^pis, Salter. PI. XV. Figs. 10-12. 



Memoirs of the Geological Survey of Great Britain (Vol. iii. 

 pp. 334, fig. 11, 1866). — This species appears to slightly exceed 

 L. ferruginea in its dimensions, and is perhaps wider in proportion to 



known fauna of the 'Menevian Gronp,' which has been proved subsequently to 

 extend not only through much of the N.-West of Pembrokeshire, but also in 

 various districts in North Wales, and always to contain the same species as those 

 first found in the district. Mr. T. Belt's valuable researches on the 'Lingula 

 Flags ' will be found recorded in Vols. IV. and V. of this Magazine. 



