EXPLANATION OF THE PLATES. 
On 
PLATE III. 
FOSSILS OF THE LINGULA BEDS OR FLAGS. 
ANNELIDA. 
Fig. 1.—CRUZIANA SEMIPLICATA, Salter. 
Proceedings of the British Association, 1852, p. 58; Siluria, third edition, p. 
45, Foss., 4, f. 53. 
From the figure in the Memoirs of the Geological Survey, vol. iii., pl. iii., fig. 
1. These peculiar markings show a series of irregular folds or ridges, 
proceeding from a central furrow and bordered on both sides by a smooth 
and bevelled edge. ‘They are, as Mr. Salter observes, generally considered 
to be fucoids, or seaweeds; he is, however, inclined to the opinion that 
they are filled-up worm tubes, or burrows. M. G.S., vol. iii., p. 292. 
Lower Lineuia FLaGs.—Carnedd-y-Filiast, near the Penrhyn slate quar- 
ries, Bangor, Maentwrog, North Wales ; also beneath the Stiper Stones, 
Shropshire ; or an allied species. 
Fig. 2.—a-d. DICTYONEMA SOCIALE, Salter, sp. 
Professor J. Hall, Paleontology of New York vol. ii., p. 174. _Graptopora. 
Siluria third ed., p. 47; Foss., 7; f., 3. Memoirs Geological Survey, vol. 
iil., p. 331, pl. iv., fig. 1. 
a. From the figure in Memoirs Geological Survey, vol. iii., pl. iv., fig. 1. 
Portion of slate, with “ fronds” grouped together, and radiating from the 
base. 
b. From the figure in Memoirs Geological Survey, vol. iii., pl. iv., fig. 1 a. 
A single example, showing the attachment, or ‘“ radicle,’” from which 
proceed the diverging branches bearing the cells, and united by processes 
or dissepiments. 
e. Original.—A smaller example, showing ring-like. process of attachment, 
and the dividing or dichotomizing branches, with crossing dissepiments 
pressed upon each other. From a specimen in the collection of the 
Geological Survey of Ireland, obtained from the railway above Plas 
Oakley, Maentwrog, Merionethshire, North Wales. 
d. From the figure in Memoirs Geological Survey, vol. iii., pl. 4, fig. 1b. 
Enlarged view, to which, however, no special reference is made in the 
text or list of plates. It shows a slightly projecting row of cells arranged 
on each side of the branches, asin Fenestella, a character which is alluded 
to by Mr. Salter at p. 332 of the same volume. 
Upprrmost Lineura Friacs.—In black slate, at Bron Foel slate quarries, 
S. W., of Tremadoc, abundant. In beds at the railway above Plas Oak- 
ley, Maentwrog, rare; Brampton Bryan Park, Pedwardine, Shropshire ; 
