MIDDLE BALA GROUP. 

Case and 
Column of 
Drawers. 
Reference to McCoy's 
Synopsis: and Figures of Genera. 
Names and References; Observations, &c. 

Gl 
G1 
Gl 
Gl 



Ling. Davisui, in part. 
Pl. 1 4, fig. 6. 
Pl. 1 1, fig. 8, p. 254. 
Pseudocrania, p. 187. 
IPiieriesile 2. 

Spirigerina, p. 197. 
a 



Numbers and Localities. 

Lingula, Bruguitre. The true Lingule appear 
to have commenced existence in the Bala 
rocks; as the Lingulelle are characteristic 
of the Middle Cambrian or Lingula Beds. 
Lingula is the most equivalve, and least 
complex of all the genera of Brachiopods, 
the muscles widely separated, the shell is 
horny and flexible, without calcareous mat- 
ter or any hinge. The spiral arms are 
fleshy only. No calcareous spires occur in 
paleeozoic rocks till we reach the Devonian 
and Carboniferous periods. ? 
Lingula ovata*, McCoy (Davidson, Mon. Sil. 
Brach. p. 38, pl. 2, figs. 19—23). [The spe- 
cimen figured is a squeezed specimen of L. 
Davisii from the true Lingula flags, p. 39.] 
Lingula tenuigranulata, McCoy (Davidson, 
Sil. Brach. p. 37, pl. 2, figs. 9—14). One of 
the largest species known in any rock. 
Lingula longissima, Pander, Beitrage, pl. 3, 
fig. 21. Day. Sil. Brach. pl. 3, figs. 28—30. 
5 
Crania divaricata, McCoy (Davidson, Mon. 
Sil. Brach. pl. 8, figs. 7—12). The genus 
Crania is world-wide from the Bala beds 
to the present day. 
Trematis (Discina) corona, MSS. A giant spe- 
cies. The genus differs from Discina by its 
marginal foramen for the byssus. 
T. punctata Sow. (Dav. Sil. Brach. pl.6, fig. 9). 
Atrypa marginalis, Dalm. (Siluria, 2nd ed. 
pl. 22, fig. 19). A common fossil in beds 
above the Bala limestone; more rare in N. 
Wales and Ireland. No hinge lne—but 
calcareous spires placed so that the spire 
lies flat in the valye—mark this genus, 

b. 202, Coniston (as L. 
Davisii); Bryn Melyn, 
Bala, true species; b. 204, 
Gelli Grin, Bala. 
a. 151, Alt-yr-Anker, Mei- 
fod. (Prof. Sedgwick and 
Mr Salter). 
a. 159, Mynydd Fron Frys, 
Chirk. 
a. 152, Bryn Melyn, Bala; 
Pont-y-glyn, Diffwys. 
b. 201, Pusgill, Dufton, 
Westmorland (Prof. Hark- 
ness). 
Horderley. 
Pont-y-glyn, Diffwys ; 
Blaen-y-cwm, Nantyr. 
* The true L. ovata, figured by McCoy from the Bala rocks of 8. Ireland, is a common and characteristic fossil of this age. 
